A rate "lock" or "commitment" is a promise from the lender to lock in a specific interest rate and a certain number of points for you for a certain period of time during your application process. This means your interest rate can't go up during the application process.
Rate lock periods can be various lengths of time, between fifteen to sixty days, with the longer spans generally costing more. You can get a longer period for your lock, but in doing so, will likely have a higher rate than you would with a shorter period
In addition to going with a shorter rate lock period, there are more ways you are able to attain the best rate. The larger down payment you can make, the lower the rate will be, because you will have more equity from the beginning. You can pay points to improve your interest rate over the loan term, meaning you pay more up front. One strategy that makes financial sense for some is to pay points to reduce the rate over the term of the loan. You pay more initially, but you will come out ahead in the end.
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