Nationwide Debt Ratio

Fannie Mae, Freddie Mac and FHA have limitations on how much they will lend a borrower with respect to their income level. This is called Debt-to-Income ratio. Standard guidelines state that their debt burden should not exceed:
31% (housing) and 43% (total)

Electronic Automated Underwriting Systems (AUS) often approve borrowers up to 55% (housing) and 65% (total) in many instances.

More than 7.5 million homeowners spend at least half of their income on housing; 19 million are above 30%. That's 53% of all homeowners with mortgages. No wonder Americans feel strained. Almost 15% of American homeowners with a mortgage are spending half of their income or more on housing costs, according to 2007 data released this week by the U.S. Census Bureau. That is up from nearly 7.1 million the year before. an estimated 10 million homeowners owe more on their mortgages than their homes are worth, according to Moody's Economy.com. More than 4 million homeowners were at least one month behind on their loans at the end of June, and almost 500,000 had started the foreclosure process, according to the Mortgage Bankers Association.

San Francisco is among 14 cities where at least 20% of homeowners with a mortgage spend half or more of their incomes on housing, an Associated Press analysis of the 100 largest U.S. metro areas has found. Other such cities include the California metro areas of Stockton, Los Angeles, Riverside, Oxnard-Thousand Oaks and San Diego. Also in the top 10 are the Fort Myers, Sarasota and Orlando areas in Florida, and New York-Northern New Jersey-Long Island. The most cost-burdened homeowners in the country live in the Miami-Fort Lauderdale-Miami Beach area: 58% of homeowners there spend 30% of their income on housing costs, and 29% spend half of their income or more on housing.