A rate "lock" or "commitment" is a lender's promise to set a particular interest rate and a certain number of points for you for a specified period of time while your application is processed. This prevents you from going through your entire application process and finding out at the end that the interest rate has gone up.
Rate lock periods can vary in length, anywhere from fifteen to sixty days, with the longer period typically costing more. A lending institution will agree to freeze an interest rate and points for a longer period, such as sixty days, but in exchange, the rate (and sometimes points) will be higher than that of a rate lock of a shorter period.
In addition to choosing a shorter lock period, there are several ways you can get the best rate. A bigger down payment will result in a lower interest rate, since you'll have more equity from the beginning. You can pay points to lower your rate over the loan term, meaning you pay more up front. One strategy that is a good option for some is to pay points to improve 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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