A rate "lock" or "commitment" is a lender's promise to set a certain interest rate and a specific number of points for you for a certain period while your application is processed. This saves you from going through your whole application process and finding out at the end that the interest rate has gone up.
Rate lock periods can be various lengths of time, between fifteen to sixty days, with the longer period generally costing more. A lending institution 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 higher than with a rate lock of fewer days.
There are more ways to get a better rate, in addition to going with a shorter rate lock period. A larger down payment will result in a better interest rate, since you're starting out with a good deal of equity. You can pay points to improve your rate over the loan term, meaning you pay more initially. One strategy that makes financial sense for many people is to pay points to bring the rate down over the life of the loan. You'll pay more initially, but you'll save money in the long run.
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