So, why isn't Ypsilanti a good long-term solution for Ann Arbor's affordable housing issues?

"It's a logical question," says Rob Krupicka, a Virginia-based consultant hired to study housing affordability in Washtenaw County.

"The challenge is that Ypsilanti is getting close to 30 percent poverty, which puts it in company with some cities that you really don't want to be in company with," Krupicka told Ann Arbor officials Monday night. "When you get close to 30 percent or more in poverty, your ability to recover from that becomes almost impossible."

If low-income people continue to concentrate in Ypsilanti while Ann Arbor grows wealthier, the result is an unhealthy imbalance, essentially socioeconomic segregation, and the region's affordable housing issues won't be solved, Krupicka said during a special joint session of the Ann Arbor City Council and Planning Commission.

"If anything, you're going to create kind of new challenges because your next-door neighbors aren't going to be economically sustainable," Krupicka said.

"You would essentially be creating kind of a constant cycle of poverty, which I know is not what anyone around this table wants."

A new report from Krupicka's firm, czb LLC, suggests the Ann Arbor area collectively needs to add 3,137 non-student affordable rental units over the next 20 years. That includes 350 in Pittsfield Township and 2,787 in Ann Arbor.

Additionally, the report suggests the Ypsilanti area must grow demand for market-rate units by 4,187 units over the next 20 years.

"They need help growing demand for their community so that they can be a better partner with you in that balance equation," Krupicka told Ann Arbor officials.

Krupicka stressed that housing affordability is not just a problem for low-income people, but also a lot of middle-income people in Ann Arbor.

He said about 30 percent of people who own homes in Ann Arbor are probably paying more in monthly mortgage costs than is considered affordable.

Affordable housing is generally considered to be housing that costs less than 30 percent of household income.

"The real issue that you see when you look at your housing data is that your rental market way overheated," Krupicka told Ann Arbor officials. "Over 56 percent of all renters are paying more than 30 percent of their income in housing, and over 32 percent of all renters pay more than 50 percent of their income in housing."

Krupicka presented data showing 94 percent of people in Ann Arbor making under $20,000 per year are cost burdened when it comes to housing.

For people making $20,000 to $34,999, 87 percent are cost burdened; for people making $35,000 to $49,999 per year, 45 percent are cost burdened; and for people making $50,000 and above, 9 percent are cost burdened.

"On the supply side, you have a real rental supply issue, and it's acute, and it is dramatic, and your college students exacerbate it," Krupicka said. "And it's making it harder and harder for working folk in your community to live there."

Krupicka said Ann Arbor isn't yet anywhere close to being as unaffordable as places like Seattle, Boston, Boulder and San Francisco, but it's headed down that path.

He said there's still a chance for Ann Arbor to grow in a way that gives everyone a chance to rise, instead of creating a concentration of wealth that drives people out.

Krupicka said the "balance problem" between Ann Arbor and Ypsilanti is the most troublesome issue the county faces.

"You are increasingly becoming a county with an area of concentrated wealth and an area of the opposite," he said.

He said communities in the country that grow the best and the most sustainably are the most socio-economically integrated.

"And you all are kind of moving in the opposite direction where you have a hot housing market and you have a not so hot housing market; and you have folks with high school degrees or less, and folks with college degrees or more," he said.

Krupicka cited statistics suggesting, since 1979, the people in the top 10 percent in Ann Arbor have seen their incomes grow by almost 20 percent, while the people in the bottom 10 percent have seen their incomes decline by almost 15 percent.

"So the first way this imbalance is manifesting in your economy is those at the top are doing much, much better, and those at the bottom are doing worse," he said, adding that equates to a lot of lost economic potential for the region.

He said affordability in Ann Arbor is partly a wage issue since one in three jobs pays too little to keep pace with housing costs.

"You need $17 an hour to pay for rent in Ann Arbor. You need $12 an hour to pay rent in Ypsilanti," he said.

"But if you don't address the supply issue, it doesn't matter how much you pay them in wages, they won't have a place to rent."

Krupicka said it's also a quality-of-life issue, as Ann Arbor depends on low- and middle-income people to provide important community services.

For every high-dollar job such as a tech engineer or doctor or lawyer, he said, the community relies on two or three mid-level workers.

"But if those folks don't have a place to live, and don't have an ability to start businesses in the community because it's too expensive, then your ability to provide the kind of services that the folks you're attracting want to see is going to diminish," he said. "The folks who are providing those services are going to feel squeezed, and their quality of life is going to get worse because their rent is going to keep going up."

He added, "And then ultimately, they're going to keep moving further and further out of the city, which is going to make traffic get worse."

Krupicka said it would take about $200 million to achieve the goal of about 2,800 new affordable rental units in Ann Arbor over the next 20 years. He said that most likely would be a combination of public and private dollars.

He encouraged Ann Arbor officials to focus their energy on getting more apartments built in the city that are affordable for people earning up to 60 percent of the area median income, or up to $36,700 per year for an individual.

"If you look at where your rental market is most overheated, and you look at where kind of your workforce is, that's the place where you have the most acute problems right now," he said, telling city officials they are in a unique position to stem the tide.

Council Member Sabra Briere, D-1st Ward, said some people think of housing for people who have no income when they hear "affordable housing," and they're afraid that it will mean crime and drugs coming into the community.

She said it's important to know what's really being talked about is housing affordability for people who make up to $36,700 per year.

Mary Jo Callan, director of the Office of Community and Economic Development, said that includes people such as dental assistants, preschool teachers, mental health counselors, court clerks and maintenance technicians.

"It's the folks who really every day make your community function," Krupicka told Ann Arbor officials.

Krupicka said Ann Arbor already puts a lot of resources toward addressing the problems faced by those on the lowest rungs of the economic ladder.

"But the place that's having the biggest effect on your economy, and over the long term on your quality of life and on your economic prospects, is that workforce level, and that's the place where you're seeing the most pain," he said. "And if you don't address it, it's what's going to hold you back."

Mayor Christopher Taylor said he was glad to hear the consultant's report. He said it articulates that affordable housing brings real benefits and improves quality of life for both those who are wealthy and those who are not so wealthy.

He called 2,800 affordable rental units over the next 20 years a "daunting" number, but he said it's something the city can work toward.

Callan said the plan is to form a regional working group with representation from each community and begin to talk about next steps.

Ryan Stanton covers the city beat for The Ann Arbor News. Reach him at ryanstanton@mlive.com or 734-623-2529 or follow him on Twitter.