New federal regulations require mortgage lenders to do what should go without saying: verify that prospective borrowers can pay.

Yet during the housing bubble, many lenders all but abandoned traditional underwriting standards, and the resulting wave of foreclosures has taken years to recede. An “ability-to-repay” rule, adopted last month by the Consumer Financial Protection Bureau and effective January 2014, is intended to protect borrowers from again falling victim to risky lending.