The housing market is in a slump, but the basic need for shelter is a constant. Enter Habitat for Humanity International – which placed sixth in Builder magazine’s survey of the largest U.S. homebuilders, with 6,032 home closings last year.

Despite the many relatively inexpensive homes for sale Habitat is filling a big gap in affordable housing. Observes Stephen Melman, economist for the National Association of Home Builders: “Affordability is close to an all-time high because of historically low interest rates and home prices rolled back about 10 years or more.” But, he adds, the requirement for “near-perfect credit scores and large down payments” are shutting out buyers.

Each of the many HFH affiliates nationwide maintain their own rules on who qualifies to buy a new or refurbished home, notes Matt Sutton, coordinator for the Clarksdale, Miss., affiliate. At the Clarksdale HFH, buyers “have to demonstrate that their current housing is substandard, that they have the ability to pay [the no interest loan], and that they are willing to be a partner,” shares Sutton. Partnering means the buyer and his friends and family must contribute at least 400 hours of labor on the home.

While low-income families are finding shelter, thousands of other Americans also are benefiting from HFH. Efforts have expanded to purchase and renovate vacant foreclosed properties and to provide repairs for existing homeowners, reports Nakia Fowler, a HFH spokesperson.

“These services are critical right now,” observes Dan Immergluck, professor at the Georgia Institute of Technology. “We face a glut of vacant homes, and Habitat buyers are one of the few sources of buyers able to purchase in many markets.”