Retirees trying to obtain a mortgage may find that a pristine credit history and healthy retirement accounts are not enough. Lenders are also looking for a consistent monthly income in line with their usual debt-to-income standards.

Sanford Evans, 75, ran up against this requirement recently when he applied for a $174,000 loan to finance the purchase of an apartment in the Riverdale section of the Bronx. With brokerage accounts exceeding $1 million, a TransUnion credit score of 822, and the ability to make a 40 percent down payment, Mr. Evans didn't anticipate any problem with qualifying.