Thirty-year, fixed-rate mortgages averaged 7.23% this week, according to the Federal Home Loan Mortgage Corp. The average was down from 7.24% last week and the lowest since it stood at 7.21% the week of Oct. 30. Rates had not been that low since they averaged 6.94% the week of Feb. 15, 1996. On one-year adjustable rate mortgages, lenders were asking an average initial rate of 5.53%, up from 5.48% last week. Fifteen-year mortgages, a popular option for those refinancing mortgages, averaged 6.78% this week, down from 6.80% a week earlier. The rates do not include add-on fees known as points.