A rate "lock" or "commitment" is a promise from the lender to freeze a particular interest rate and a particular number of points for you for a certain period during your application process. This ensures that your interest rate can't grow 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. A lender will agree to lock in an interest rate and points for a longer period, like sixty days, but in exchange, the rate (and sometimes points) will be more than with a rate lock of fewer days.
In addition to opting for the shorter rate lock period, there are other ways you are able to get the lowest rate. A bigger down payment will result in a lower interest rate, since you will have a good deal of equity from the beginning. You can pay points to bring down your rate for the loan term, meaning you pay more up front. For a lot of people, this is a good option..
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