Mortgage rates have been so low for so long that it's created a lock-in effect where people don't want to sell their homes to buy new ones for fear of losing their attractive rates. That's made it "almost impossible" for first-time homebuyers to enter the housing market, U.S. Treasury Secretary Janet Yellen said during her testimony before the House Ways and Means Committee. "With house prices having gone up and now with much higher interest and mortgage rates, it's almost impossible for first-t