Mark Zeigler was leaving the country a couple years ago and wondering what to do with his vehicle.

So the Denver resident rented his 2008 Toyota 4Runner to a host of strangers.

“The whole time I was gone, I was earning money,” Zeigler said.

As the shared economy booms with millions renting other people’s homes, tools and even pets, it’s not surprising to see a company such as RelayRides thriving.

In the past five years, the California-based company has morphed from an hourly rental model into a competitor with Avis, Hertz and Enterprise, with car owners in 2,500 cities listing their vehicles for rent. And Denver, where RelayRides has been since 2012, is one of the company’s top five hottest markets.

It’s a simple model, much like the home-renting juggernaut Airbnb: People list their cars. Prescreened drivers rent the cars. Reviews posted online by both sides grease future transactions.

“I would say RelayRides is the Airbnb of cars,” said Steve Webb, the company’s buzzword-dropping spokesman. “We are taking the rental car experience, which is a very corporate, faceless experience, and making it more aspirational, like Airbnb has done for accommodations. We are empowering people to create their own opportunities.”

One big difference is that company founder Shelby Clark — a Denver native with a master’s degree in business administration from Harvard — developed a one-of-a-kind insurance product that protects the car when it’s rented.

It’s usually the first question people have they ponder listing their cars and trucks on RelayRides, Webb said. “This marketplace doesn’t work without this insurance.”

The insurance policy provided by RelayRides becomes the primary policy when a car is rented. It provides $1 million in liability plus the cash value of your car in case of an accident. And owners have the ability to screen drivers with access to online reviews and driving records before renting their vehicles. Owners also set their own price and mileage limits.

Renters pay RelayRides a fee — 10 percent of the rental price — that covers the cost of the liability insurance policy. The car renters also choose their own levels of coverage protection with different insurance packages, not unlike those offered by traditional rental car agencies.

The insurance policy and the reviews of renters posted by other owners alleviated Zeigler’s concerns about handing over his car to someone he didn’t know. The money helped too.

“If I really wanted to, I could pay for the car just from this. It’s been more than paying for itself,” said Zeigler, who has rented his $125-a-day 4Runner one week a month for the past two years. “It’s good money for not doing too much.”

Most owners offer to pick up their renters — for a fee — at the local airport. Some renters take a taxi or shuttle to the owners’ homes.

The biggest appeal over traditional rental car agencies is the price, Webb said. RelayRides vehicles rent for, on average, 35 percent less than rental car companies. The website lists 157 cars, trucks and vans for rent in Denver, with prices ranging from $23 a day for a 1993 Toyota Tercel to $175 a day for a loaded 2014 BMW X6. The selection runs the gamut, from all-wheel drive, winter-ready cars and trucks to fuel-efficient grocery-getters for around town.

Robert Martin and his wife spent a year in Denver living without a car, occasionally renting a vehicle through traditional companies. On a weekend when those companies were sold out, he tried RelayRides, renting an Audi A4.

In January 2014, he and his wife put their 2014 Mercedes-Benz CLA-Class on the RelayRides market. It has rented often at $65 a day.

“Our car is essentially free to us, which was exactly what we were aiming for,” Martin said.

Denver is a busy hub for RelayRides renters and owners, Webb said. But while most of the company’s rentals in big cities such as San Francisco and Chicago are delivered to an even split of visitors and locals, Denver’s renters are largely visitors.

“Our people in Denver are specifically renting to people who have come to Colorado to travel,” said Webb, describing a recent meet-up with Denver owners where several longtime RelayRides listers said they were planning to put a second car into the market. “Their cars could be rented out all the time if they wanted.”

Shahana and Mark Ali have rented their 2013 Nissan Xterra almost every week since they put it in the RelayRides market in late December. Every renter has been a vacationer heading into the mountains.

“We are renting it more than I thought we could,” Shahana said. “I can definitely see how this could be a source of income.”

The couple, who rented out their Lower Downtown loft via Airbnb last year, often pick up their renters at the airport.

They married in October, and the revenue from renting their SUV not only covers the monthly payments and insurance, it’s also helping to pay down the cost of their wedding.

“We are true believers in the shared economy,” Shahana said.

Jason Blevins: 303-954-1374, jblevins@denverpost.com or twitter.com/jasonblevins