Families wait years to get off the government's waiting list for a rental voucher, sometimes while living in a homeless shelter. When they finally get that housing aid, they often struggle to find landlords willing to rent to them.

Most landlords screen out people who have a criminal background, poor credit or a history of evictions, making it difficult for voucher holders to find somewhere to live, even when they can afford rent. In fact, it's common for people to lose their vouchers -- which have expiration dates -- after months of unsuccessful searching for a home.

To ease landlords' worries and house more of the homeless, a growing number of cities are offering to reimburse landlords for certain losses -- unpaid back rent or repairs for tenant-caused damages -- that result from accepting applicants who have rental vouchers.

“Many, many communities are doing this, and it’s out of necessity,” says Elisha Harig-Blaine, who works on affordable housing issues at the National League of Cities. “They simply can’t get people placed into housing with these subsidies.”

This month, Boston and the District of Columbia announced their own “housing guarantee” or “risk mitigation” programs.

In Boston, the city will reimburse landlords for up to $10,000 in unpaid back rent or property damages that go beyond normal wear and tear. In D.C., a nonprofit is raising $500,000 in private funds to cover up to $5,000 in landlord costs per tenant. In both places, program staff will be available to address landlord complaints and provide case management for the tenants.

The question is, will that be enough to convince landlords to accept tenants who pay with rental vouchers?

In many of the cities that have these programs, affordable housing is hard to find, but renters with clean criminal and financial backgrounds are not.

“At the end of the day, real estate is a business. These landlords want to do the right thing, but we’re talking about their livelihood," says Harig-Blaine, who has attended landlord recruitment events in nine communities across the country.

Landlords, he says, don’t want to deal with missed payments or other trouble that might come with renting to someone who was recently homeless.

Nevertheless, local officials in D.C. -- which is getting 800 new residents every month and has some of the country's highest rents -- are optimistic.

“Rather than [renting] to the millennial who is just moving in from some other part of the country," Neil Albert, president and executive director of the DowntownDC Business Improvement District, the nonprofit raising the money, told Governing. Albert thinks the risk funds will spur landlords to "weigh our needs and give equal consideration" to voucher holders.

There is no official number of landlord assistance programs, according to the U.S. Interagency Council on Homelessness, but they exist in Denver, Fargo, N.D.; Marin County, Calif.; Orlando, Fla.; Portland, Ore.; and Seattle-King County, Wash, which started one of the first almost a decade ago. Some states, such as Minnesota and Oregon, offer them as well.

Before launching its program, Boston researched them in other cities and found that participating landlords rarely had to use the risk funds, according to Boston's Department of Neighborhood Development. Last year, in Seattle and King County, for example, participating landlords filed mitigation claims for only 15 percent of the renters covered by the program. Data on how many landlords participate in each city and how many people are housed through such programs, however, is not readily available.

D.C. officials, though, expect demand for the risk funds to be higher in their city.

"We think it will be a little different here in D.C. We think people will actually use this fund,” says Albert, adding that if it results in more units being rented to voucher-holders, then “that’s a great problem to have.”

One difference between the Boston and D.C. landlord programs is the funding and management structure. In Boston, the city is putting up the risk funds and managing its landlord relations on a two-year pilot basis. In D.C., a nonprofit business improvement district is raising funds -- mostly from developers -- and a local housing nonprofit is administering the program. That's because landlords and property managers in D.C. pushed for a privately managed fund that could provide reimbursements faster than a government agency, says Albert.

More than 5 million Americans receive some kind of rental voucher from the state or federal government, according to the Center on Budget and Policy Priorities. In general, households must be below the federal poverty line or make less than 30 percent of the area median income to qualify for housing assistance. Because the program is not an entitlement, less than a quarter of all eligible families receive housing assistance, and many households wait years before a voucher becomes available.

Landlord assistance programs are trying to address a chicken-and-egg problem, says Laura Zeilinger, D.C.’s director of human services. Landlords want renters who have jobs and earn a steady income. But stable housing is usually the first step to helping people get and keep a job. She’s hoping that landlords in D.C. will waive income requirements in their applications.

“Housing is an important foundation for people to be able to work and to achieve their potential,” she says. “It’s a really difficult thing for people to do while living in a shelter environment.”