When it comes to real estate, gentrification might just be the touchiest subject of all. In search of reasonable housing prices, short commutes, and the tantalizing prospect of a kick-ass return on investment, professionals are moving en masse into lower-income neighborhoods. But while these newcomers often rehab old and vacant homes and bring a rush of investment to the community, many long-term residents and business owners don't get to experience the booms—they get priced out of the very neighborhoods they helped build.

Still, the tsunami of gentrification, having utterly transformed some of the biggest cities on each coast (hello, New York and San Fransisco!), continues to wash over the nation, an inexorable force. Accelerated by sky-high rents and home prices as well as a wave of urban renewal, it's now hitting previously overlooked neighborhoods. For home buyers, it's an opportunity—and a challenge. Those who time it right and buy homes in places on the early cusp of gentrification can get in cheaply, and be assured of a big windfall down the road.

So the realtor.com® data team set out to find the fastest-gentrifying neighborhoods in the U.S. We wanted to identify the places on the upswing now.

“Neighborhoods that are well located, with public services and transportation that were originally built for the middle class, are the ones more likely to be gentrified,” says Phillip Clay, professor emeritus at the Massachusetts Institute of Technology and author of “Neighborhood Renewal: Middle-Class Resettlement and Incumbent Upgrading in American Neighborhoods."

The neighborhoods gentrifying the fastest today are still in big cities, but they're mostly secondary markets with room to grow, packed with affordable historic homes, and usually located near overpriced urban hot spots.

Clay takes an unvarnished view of urban gentrification: "Vacant land is developed," he says. "That’s an active gain for the city. And commercial activity increases." But with it comes higher prices all around.

“For longtime residents, the only people who are winners are those who are in a position of cashing out," he adds.

To find the fastest-gentrifying neighborhoods, we looked at lower-income ZIP codes in America's 100 largest cities. We excluded ZIPs that were more expensive than their city's median sale price back in 2012 as well as those with few home sales in the years we measured. Then we created our ranking based on the changes in the following metrics from 2012 to 2017:

Change in median household income

Change in median home sale price

Change in the share of residents over 25 with a bachelor's degree or higher

Change in the share of residents over 25 with a master's degree or higher

Change in median home listing price on realtor.com*

We limited the ranking to just one ZIP code per city. Got it? Let's take a tour of some places that are changing fast.

Fastest-Gentrifying Neighborhoods Claire Widman

Rivertown (Detroit, MI) realtor.com

ZIP code: 48207

Median list price: $193,000

5-year median sale price change: +526.4%

5-year median household income change: +17.5%

5-year change in the share with bachelor's or higher degree: +53.9%

At the start of the decade, empty warehouses and factories lined the Detroit River in the Rivertown-Warehouse District. But the once-blighted neighborhood has been undergoing a development boom in recent years as a result of the spillover from the Motor City's downtown renaissance. Young professionals looking for cheaper cribs moved a little farther east into Rivertown.

"There wasn't much there 10 years ago. You didn't go there at night," says Thomas Nanes, a real estate agent at Community Choice Realty Detroit. "Or during the day."

This decade the area has transformed from largely commercial to residential. The community is now filled with converted lofts, low-rise condominium buildings, cocktail bars, and food trucks. One-bedroom lofts with exposed brick in century-old, industrial buildings in Rivertown can top $300,000. That's quite a transformation.

But these high prices have caused buyers to look farther north in the ZIP code, which goes up to Warren Avenue, a low-income residential area. Now, much to the dismay of longtime residents, prices are rising fast in the area as investors snap up 1920s-era, Craftsman-style homes, some of which have sat vacant for years. Many of these homes require significant repairs, which can top $150,000.

"As development moves north, more people will get displaced," Nanes says.

Little Haiti/Liberty City (Miami, FL) realtor.com

ZIP code: 33127

Median list price: $375,100

5-year median sale price change: +205.9%

5-year median household income change: +23.6%

5-year change in the share with bachelor's or higher degree: +87.8%

It isn't rising home prices or access to public transit that's led to the big changes in the Little Haiti/Liberty City area; the driving force is what local activists call "climate gentrification." Rising sea levels and sky-high flood insurance rates are a huge deal in Miami. (The city was named the nation's most vulnerable to hurricanes by AccuWeather.) So developers have turned to lower-income neighborhoods like Little Haiti and Liberty City, which are farther from the beach and at a higher elevation.

"Folks are moving from the beaches and moving inland into this black and brown community on high ground," says Trenise Bryant, chair of the Miami Workers Center and who grew up in public housing in the area. "People here are getting pushed out and priced out."

For much of the decade, builders were busy putting up condo buildings, craft breweries, and bistros in Wynwood, the southern section of this ZIP code. But over the past few years investors have set their sights on homes in Little Haiti and Liberty City, where homes can still be found for under $250,000. But prices will only go up. City officials are currently considering a $1 billion development called the Magic City Innovation District, which would span seven blocks and include new residential buildings.

Lockwood (Charlotte, NC) realtor.com

ZIP code: 28206

Median list price: $280,000

5-year median sale price change: +100.9%

5-year median household income change: +28.5%

5-year change in the share with bachelor's or higher degree: +61.8%

The influx of new companies and residents into Charlotte, which boasts reasonable home prices and a low cost of living, has led to a housing shortage. That has spurred a big spike in home flippers mailing flyers and going door to door in poorer neighborhoods near the city center to find properties to rehab and resell or rent out.

Lockwood, less than a 10-minute drive from downtown, has become ground zero for investors despite once being known as one of the most dangerous places in the country. The area has lots of homes built in the 1940s with large back and front yards. Prices are quickly nearing $300,000.

But these changes aren't welcome by everyone in this predominantly low-income, black neighborhood. Some tenants have been evicted as their apartment buildings are redeveloped into pricey condos.

Johnston Terrace (Austin, TX) realtor.com

ZIP code: 78721

Median list price: $424,000

5-year median sale price change: +148.2%

5-year median household income change: +29.5%

5-year change in the share with bachelor's or higher degree: +69.6%

As wealthier Austinites have moved farther east into poorer communities in search of good real estate deals, it has created tension with many longtime residents.

Folks are now moving into Johnston Terrace, just east of Interstate Highway 35—Austin's historic barrier between white and brown communities. That's because the median home price in Austin has climbed 20.2% over the past five years.

"People want to be in a young, hip neighborhood that’s still close to work. Johnston Terrace is checking all those boxes," says real estate broker Brad Pauly of Pauly Presley Realty. "Trendy restaurants and bars are opening up. Upscale hotels are being planned."

Folks are buying inexpensive foreclosed homes in the area and fixing them up. That's changing the demographics of the community: The percentage of white residents doubled from 2011 to 2017, to 20.6%.

"Rising property taxes and an increased cost of living have forced people out of their longtime homes," says Liz Jeneault, a former local news anchor who moved away in March in part because the city has become so expensive. "Those homes are often torn down once they leave and are replaced with luxury condos."

Downtown/Patterson Green (Raleigh, NC) realtor.com

ZIP code: 27601

Median list price: $450,000

5-year median sale price change: +58.5%

5-year median household income change: +57.4%

5-year change in the share with bachelor's or higher degree: +58.3%

Many of the younger techies moving to Raleigh want to be in walkable communities. They've descended on the city's downtown and historically lower-income neighborhoods like Patterson Green. This area is home to Bida Manda, a restaurant that was named the best in North Carolina in 2016 by Business Insider, and the North Carolina Museum of History.

"This was a predominantly African American neighborhood, and many of these folks [have] been completely priced out," says local real estate agent Terri Taylor of Fathom Realty, in Raleigh. "Many of the new apartments in the area cost upward of $2,000 per month. For many long-term residents, that’s a huge stretch compared to how things used to be."

Developers in these communities have torn down older homes to put up larger houses with wide porches and high-end finishes or new apartment and condo towers. Units at the Fairweather, a low-rise condo building, range from $400,000 to $1.5 million.

Uptown (Oakland, CA) realtor.com

ZIP code: 94612

Median list price: $695,100

5-year median sale price change: +128.2%

5-year median household income change: +63%

5-year change in the share with bachelor's or higher degree: +26.3%

Even six-figure-income families can feel poor in San Francisco. That's why many are heading to across the bay to Oakland, the formerly crime-riddled community in the East Bay. In recent years the Uptown neighborhood has become the city's entertainment hub, anchored by the overhauled Paramount Theatre, an art deco building that's now home to Oakland East Bay Symphony, the Oakland Ballet, and dozens of other live performances each year.

"People start to ask themselves, 'Do I want to spend $3 million for a townhouse, or do I want to spend one-tenth of that and still be a commutable distance to my job?'” says Chunlei Liu, a real estate agent with Climb Real Estate.

In 2012, the median home price in Uptown was $315,000. Now, the cheapest abode on the market is a 600-square-feet, one-bedroom condo priced at $499,000.

"We have a lot of properties that were neglected for a long period of time. When developers or even investors come in and make upgrades on those properties and pay the property taxes, it makes the city better," says Liu. But "there's definitely community blowback. ... People can’t afford to live in the neighborhoods where they once were."

Encanto Village (Phoenix, AZ) realtor.com

ZIP code: 85006

Median list price: $315,100

5-year median sale price change: +98.3%

5-year median household income change: +53.1%

5-year change in the share with bachelor's or higher degree: +61.5%

No city in America has more residents moving in than Phoenix. They're coming to escape high costs in places like California, for better jobs or because they want to retire someplace warm where their dollars will stretch.

But all those new faces are changing the character—and affordability—of the city's neighborhoods. Over the past few years, the eastern section of Encanto Village, where residents have the lowest household incomes, has experienced some of the biggest price hikes. Buyers are drawn to its bungalow-style homes built in the 1920s in the Coronado Historic District and priced for around $300,000. This area is just a short walk to several light-rail stations, and lots of new coffee shops and nightlife venues

"New condos and apartments drove up prices. ... Longtime residents are taking advantage of increased prices and getting significant returns [on the sales of their homes]," says Sue Flucke, president of Phoenix Realtors®. Many of these sellers are taking off for affordable suburbs outside the city.

Lawrenceville (Pittsburgh, PA) realtor.com

ZIP code: 15201

Median list price: $350,000

5-year median sale price change: +118.7%

5-year median household income change: +34.4%

5-year change in the share with bachelor's or higher degree: +73.6%

Spencer Schmidt was paying just $950 a month for his two-bedroom rental when he moved to Lawrenceville, a historic working-class Steel City neighborhood on the Allegheny River, three years ago. Now, after a steady stream of new residents bid up the prices on a limited supply of rentals, the 25-year-old is dropping $1,600 a month on a different two-bedroom rental.

“There are a lot more young professionals here now—more young people walking their dogs, fewer established Pittsburgh families,” says Schmidt, a systems analyst at a Pittsburgh insurance firm.

Over the years, the area has become popular for its close proximity to downtown and cool vibe. In the late 1990s, the free festival Art All Night was launched. The neighborhood is now filled with cafes, bars, and breweries such as the 11th Hour Brewing Co., a 20-barrel brewhouse.

Remodeled row homes built at the turn of the 20th century with private backyards go for over $350,000. The sections of the ZIP code closer to downtown have the highest prices, while homes for under $150,000 can be found toward its outskirts.

Olde Kensington (Philadelphia, PA) realtor.com

ZIP code: 19122

Median list price: $312,300

5-year median sale price change: +88.9%

5-year median household income change: +47.2%

5-year change in the share with bachelor's or higher degree: +61.9%

The gentrification of Fishtown is legendary in Philly. The former working-class neighborhood is now packed with hipsters, beer gardens, and a hot music scene. But as real estate prices have surged, folks are looking at more affordable nearby communities like Olde Kensington and Norris Square, which are lined with historic row homes.

Those lower prices persuaded real estate agent Rachel Shaw, 34, to rent out her 800-square-foot home in Fishtown this year and buy a 2,200-square-foot foreclosure in Norris Square. The row home is a short walk from Norris Square Park, a green space that host arts and community events. Some longtime residents are moving to other nearby communities where rents are still low.

"We're seeing a lot of first-time home buyers here," says Shaw, of Philly Home Girls. "You get more for your money, and there are still lots of young professionals and creative types."

Eastside Promise Neighborhood (San Antonio, TX) realtor.com

ZIP code: 78202

Median list price: $220,000

5-year median sale price change: +78.5%

5-year median household income change: 8.8%

5-year change in the share with bachelor's or higher degree: 77.5%

Austin isn't the only Texas city attracting millennials and tech companies. San Antonio, about 80 miles southwest of the state capital, has also seen a slew of new residents. They're driving up prices in Eastside Promise Neighborhood, a predominantly Hispanic community near downtown.

"You aren’t seeing the people you used to. In this neighborhood, you could go block to block and know every face. But now it's very different,” says Lusi Denis, a real estate agent at Century 21.

Homes closer to downtown, like this 1930s bungalow priced at $274,900, have seen the largest price increases. However, there are some single-family homes at the edges of the area where buyers can find something under $100,000. But all of those new residents have come at a cost.

“Families that have been here for generations are leaving. It’s tragic to see," Denis says.

* The change in median home listing price on realtor.com was from 2013 to 2017, instead of 2012 to 2017 like the other metrics. This was due to incomplete 2012 data.

Clare Trapasso and Allison Underhill contributed to this report.