CNNMoney says mortgage rates are low and houses are cheap, but only the well-heeled borrowers qualify, and they typically need 20 percent down.  The Federal Reserve says 25 percent of people who apply for financing are turned down, even good borrowers with one of two late payments are being denied.  Some potential buyers are not even applying because they sense it is futile to even try.  The average credit score for Fannie Mae and Freddie Mac loans has risen 40 points, and loans for scores under 620 rarely exist.  One report suggests the tighter restrictions may have excluded 30 percent of potential buyers from the market.