David H. Stevens, president of Long & Foster, the Washington real estate firm, is expected to be nominated tomorrow to run the Federal Housing Administration. Though the Obama administration declined to confirm the appointment today, sources said Stevens has been undergoing the required background checks. These sources spoke on condition of anonymity because they did not have the administration's permission to speak publicly. If confirmed by Congress, Stevens would be the only FHA commissioner in recent years with a strong background in single-family home mortgages. After more than two decades in the financial services industry, Stevens has overseen every aspect...