A rate "lock" or "commitment" is a lender's promise to freeze a particular interest rate and a particular number of points for you for a specified period of time while your application is processed. This prevents you from working through your whole application process and discovering at the end that the interest rate has gone up.
Rate lock periods can be various lengths of time, anywhere from fifteen to sixty days, with the longer ones generally costing more. The lender will agree to lock in an interest rate and points for a longer period, say sixty days, but in exchange, the rate (and sometimes points) will be more than that of a rate lock of a shorter period.
There are more ways to get a lower rate, in addition to agreeing to a shorter rate lock period. A bigger down payment will result in a lower interest rate, since you are starting out with more equity. You can pay points to bring down your interest rate for the loan term, meaning you pay more up front. To a lot of people, this makes sense and is a good deal..
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