But in Los Angeles, where having a car is as essential as owning a home, many are sleeping in their vehicles to ensure a roof over their head.
Campaigners for the homeless expect more to hole up in their cars as they lose homes due to the problems that have dogged "subprime mortgages" - those granted to low-earners with little capital of their own.
The trend comes despite the fact that sleeping in a car is illegal in the Los Angeles area.
"The subprime meltdown is the kind of situation that pushes people into cars. It's a very common story," said Ruth Hollman, of Self-Help And Recovery Exchange, a group that helps homeless people.
Advocates hope Los Angeles will adopt programmes in place in cities such as Eugene, Oregon, and Santa Barbara, California, that enable people to live in cars while receiving services they need to get back on track.
"It's an old saying in social services that most people are one to six paychecks away from being homeless. But if you can't make your mortgage, it's more like a month or two," said William Wise, of the relief agency St Vincent de Paul of Eugene, which works to find overnight parking spots for homeless people.
Without such spots, people forced to sleep in their cars fear being towed and ticketed by police, as well as being attacked by thugs and facing public scorn.
Emily Love, 61, was sleeping in her car in Marina Del Rey, California, when two youths smashed her windscreen with a shopping trolley. A week later, she was back in the car.
After her car was attacked, the former teacher sat staring at the shattered glass. "I don't like to talk to the cops. They don't like people sleeping in their cars," she said in her car crammed with her possessions, including two cats.
Government figures say there are about 754,000 homeless people in the US, about 300,000 more than available beds in shelters and transitional housing.
Many of the temporarily homeless get into deeper trouble because they try to keep it quiet and do not seek help.
Philip Mangano, of the US Interagency Council on Homelessness, said he strongly opposed programmes that sanction living in cars.
"It's a national tragedy that we are resorting to these plans. It doesn't measure up to the promise of America," he said.
Mr Mangano has been working with cities to develop ten-year plans to end vagrancy through a new business- oriented approach that has cut homelessness in cities such as San Francisco and Philadelphia.
The number of people living in cars is hard to calculate, but Ruth Hollman said a recent estimate of 1,000 in Los Angeles was far below the actual figure. She said some people living in their cars pay gym memberships so they can shower, and attend training courses or have jobs. "One man I know goes to college and people there don't even know he's homeless," she said.