Nearly 4,800 subprime loans made to Bay Area borrowers in 2006 are likely to fall into foreclosure in the next couple of years, costing homeowners, cities and lenders as much as $1.5 billion, according to an advocacy group for lower-income families.

Such scary statistics are prompting more cities to call upon lenders to modify problem loans and curtail what are termed predatory practices.

At the same news conference where local officials with the Association of Community Organizations for Reform Now (ACORN) released its foreclosure study Tuesday, San Francisco Supervisor Tom Ammiano introduced a nonbinding resolution urging the country’s 25 largest subprime lenders and loan servicers to agree to a three-month suspension on foreclosures of owner-occupied homes in San Francisco.

The sales rate for previously owned single-family homes dropped to its lowest level in about 10 years, and the price of resale single-family homes, condos and co-ops dropped 4.2 percent year-over-year in September, the National Association of Realtors reported today.

The trade group also reported that the for-sale inventory of single-family homes reached 10.2 months in September, which was the highest level since February 1988 when it was 10.3 months. The inventory is a measure of how many months it would take to exhaust the for-sale supply of resale single-family homes at the current sales rate.