MANASSAS -- New anti-illegal immigrant policies could worsen an already weak real estate market in Prince William County, agents and mortgage lenders say.

"If I'm not welcome somewhere, I'm going to sell my house," said Jose Luis Semidey, a real estate agent whose business in the county shut down in August when he laid off 40 employees and moved the company to Reston.

He said efforts to deny certain public services to illegal immigrants "have accelerated the collapse of the real estate market in the minority community."

From August 2005 to August 2007, home sales fell 66 percent in Prince William County, and the number of properties on the market more than doubled to more than 6,500.

About 900 of the homes on the market in August were bank-owned or sliding into foreclosure -- a tenfold increase from 2005, said Michael Minnery, president of the Prince William Association of Realtors. Many of those houses are in areas with high concentrations of Hispanic residents.

Several lenders who work with Hispanic immigrants say that not long ago, customers with little more than a tax identification number and a pay stub were able to secure 100 percent financing on mortgages.

With little equity in their properties and adjustable-rate mortgages adjusting sharply upward, some immigrant families are walking away from their homes in the middle of the night, several real estate agents have said.

The Prince William County Board of Supervisors has not discussed the potential impact of the measures on the county's housing market, said Supervisor W.S. Covington. But he said the county would save on school expenditures and other costs if thousands of illegal immigrants leave.

"I don't see it as a bad thing," he said.