mortgage rates have backed off the sixmonth high they reached a week ago the average rate on the standard 30year fixed mortgage slipped to 671 according to a survey of lenders released thursday by mortgagefinance giant freddie mac a week ago mortgage rates were 679 the highest level since they briefly topped 7 this fall higher mortgage rates can sharply push up the monthly cost to buy a home putting homeownership out of reach for some around twothirds of wouldbe homebuyers say high mortgage rates are keeping them on the sidelines of the market according to a recent bmo financial group survey mortgage rates were just above 5 a year ago