Interest rates on the 30-year fixed-rate mortgage change all the time, so today's rate probably isn't the same as last month's or next month's. If you've found the home you want, you might as well take the plunge. On January 3, 2014, the average interest rate for a 30-year fixed-rate mortgage was 4.63 percent nationwide. By October 17, the rate fell to 4.03 percent and remained there for a week or more. It was the lowest level since June 2013 according to the mortgage-information website HSH.com. Demand for home loans surged, but the increase was driven by homeowners seeking to refinance existing mortgages. When interest rates drop, here's how to take advantage of them First, figure out what the best rates are in your area. The gap between the lowest and the highest rate a mortgage applicant is offered averages about 0.30 percentage points, according to mortgage lenders. On a $400,000, 30-year fixed-interest rate loan at 4.03 percent, borrowers will pay $145,000 in interest over the first 10 years of the loan and $289,969 in interest over the life of the loan. Calculating With a 3.73 percent interest rate, borrowers will pay $11,464 less in the first 10 years and $24,717 less over 30 years. Following the $400,000 example, a person with a FICO score higher than 740 on a scale that ranges from 300 to 850, who is paying 20 percent down, could get a mortgage at 3.75 percent interest from an online lender or 4.07 percent from local lenders. Some banks charge less if you have a savings account or brokerage account with them. Once you find a rate that appeals to you, figure out how much you'll pay per month and whether that amount is manageable.