WASHINGTON (AP) -- The government is cracking down on companies that advertise help for troubled homeowners but often turn out to be scam artists.

The Federal Trade Commission said Thursday it would propose to ban those foreclosure rescue services from collecting payment up front. Instead, they could only collect money if they were successful in providing help.

Government officials say unscrupulous companies often charge upfront fees as high as $3,000 for help with loan modifications that rarely pay off. The government says it has filed charges against 28 companies, which often imitate government housing assistance programs.