U.S. mortgage rates are the lowest in at least four decades, with a 30-year fixed loan available at 4.09 percent. That didn't help Alexis Wolf buy a town home in Beaverton, Ore. “Unless you have family help, you're stuck renting,” said Wolf, 26, a real estate broker who turned to relatives for a loan because she didn't have the credit and employment history needed to qualify for a mortgage. Wolf's experience illustrates the predicament for Federal Reserve policy makers as they end a two-day meeting today to consider ways to boost economic growth. Low interest rates, the traditional medicine for a flagging economy, aren't helping housing, which since 1982 has aided every recovery except the current one.