A rate "lock" or "commitment" is a lender's promise to set a specific interest rate and a specific number of points for you for a certain period of time while your application is processed. This means your interest rate will not go up while you are working through the application process.
Rate lock periods can vary in length, anywhere from fifteen to sixty days, with the longer spans typically costing more. A lending institution may agree to lock in an interest rate and points for a longer period, say sixty days, but in exchange, the rate (and sometimes points) will be more than with a rate lock of a shorter period.
In addition to going with the shorter rate lock period, there are several ways you can get the best rate. A bigger down payment will give you a reduced interest rate, because you are starting out with a good deal of equity. You can pay points to reduce your rate for the loan term, meaning you pay more up front. One strategy that is a good option for some is to pay points to reduce the interest rate over the term of the loan. You'll pay more up front, but you'll come out ahead in the long run.
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