Coruscation

But even the best-qualified buyer can be denied a loan if the building he or she wishes to buy into is deemed a risk.

Melissa Cohn, the president of Manhattan Mortgage, said, "The biggest issue that we have is that a large number of buildings in the city don't meet Fannie Mae guidelines."

Over the last two years, Fannie Mae and Freddie Mac have tightened the regulations that govern the loans they buy from lenders.

Fannie now requires that some condominiums carry more insurance, for example, and a new I.R.S. requirement keeps the agency from acquiring mortgages made in buildings where more than 20 percent of the square footage is commercial -- space that is used for, say, a hotel or a doctor's office.

But many of the guidelines that New York City apartment buildings don't meet have been in place for years. Fannie and Freddie guidelines have long held, for example, that no single person or entity can own more than 10 percent of the units in an established condo or co-op building. During the boom, that didn't matter much. Investors were hungry to buy bundled residential mortgages, and banks could bypass Fannie and Freddie and sell the loans elsewhere. Now, Fannie and Freddie are by far the biggest game in town, so on conforming loans, their rules are gospel.

Andrea Mottola ran into the problem of a building cold-shouldered by banks last year, when she was trying to sell her daughter's two-bedroom apartment in a condo on West 58th Street.