A rate "lock" or "commitment" is a lender's promise to hold a particular interest rate and a certain number of points for you for a certain period while your application is processed. This protects you from getting through your entire application process and learning at the end that the interest rate has gone up.
Rate lock periods can vary in length, between fifteen to sixty days, with the longer spans typically costing more. The lender may agree to freeze an interest rate and points for a longer period, like 60 days, but in exchange, the rate (and sometimes points) will be more than with a rate lock of a shorter period.
In addition to opting for the shorter lock period, there are several ways you are able to score the best rate. A bigger down payment will result in a lower interest rate, since you'll have a good deal of equity at the start. You may opt to pay points to lower your interest rate over the loan term, meaning you pay more initially. One strategy that makes financial sense for some is to pay points to reduce the rate over the life of the loan. You'll pay more up front, but you'll save money, especially if you keep the loan for a long time.
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