Rates for most types of mortgages tracked by Freddie Mac hit record lows this week, with 30-year fixed-rate mortgages averaging 4.69 percent with an average of 0.7 point for the week ending June 24.That's down from 4.75 percent last week and 5.42 percent a year ago, and beats the previous record set of 4.71 percent set during the week of Dec. 3. Freddie Mac has been tracking rates on 30-year fixed-rate loans since 1971.Turmoil in financial markets has made mortgage-backed securities that fund most home loans attractive to investors. That,  coupled with slack demand for mortgages, has helped keep rates low.Rates for 15-year fixed-rate mortgages also hit a new low in records dating to 1991, dipping to 4.13 percent with an average 0.6 point. That's down from 4.2 percent last week and 4.87 ...