A rate "lock" or "commitment" is a lender's promise to lock in a particular interest rate and a particular number of points for you for a specified period while your application is processed. This protects you from working through your entire application process and learning at the end that your interest rate has gotten higher.
Rate lock periods can vary in length, anywhere from 15 to 60 days, with the longer period typically costing more. A lending institution may agree to hold an interest rate and points for a longer period, say sixty days, but in exchange, the rate (and sometimes points) will be higher than that of a rate lock of fewer days.
There are more ways to get a low rate, in addition to opting for a shorter rate lock period. The bigger the down payment, the better the interest rate will be, as you will have more equity from the beginning. You may choose to pay points to improve your rate for the loan term, meaning you pay more up front. One strategy that makes financial sense for many people is to pay points to bring the rate down over the term of the loan. You'll pay more initially, but you'll save money, especially if you keep the loan for a long time.
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