When you're promised a "rate lock" from the lender, it means that you are guaranteed to get a set interest rate for a determined period while you work on the application process. This ensures that your interest rate won't get higher during the application process.
Rate lock periods can be various lengths of time, anywhere from 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 span of time, say 60 days, but in exchange, the rate (and sometimes points) will be higher than that of a rate lock of fewer days.
There are other ways to get a lower rate, in addition to opting for a shorter rate lock period. The bigger down payment you make, the better your interest rate will be, as you will be entering the loan with more equity. You can pay points to improve your rate for the loan term, meaning you pay more up front. To many people, this is a good option..
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