Homebuyers who have a credit score of 580 or better and a down payment of at least 3.5 percent of the home's purchase price might seem like good candidates for an FHA loan, insured by the Federal Housing Administration. But whether these borrowers will qualify for such a loan isn't quite so simple.

On paper, the FHA allows a minimum credit score of 500 if the borrower makes a down payment of at least 10 percent of the purchase price. Borrowers whose scores are 580 or higher can qualify with a 3.5 percent down payment.