When you're promised a "rate lock" from your lender, it means that you are guaranteed to keep a set interest rate over a determined period for your application process. This protects you from getting through your entire application process and learning at the end that your interest rate has gone up.
Rate lock periods can vary in length, between 15 to 60 days, with the longer spans generally costing more. A lending institution will agree to hold 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 fewer days.
In addition to opting for the shorter rate lock period, there are several ways you may be able to attain the lowest rate. The larger down payment you make, the better the rate will be, because you will be starting with more equity. You could opt to pay points to bring down your rate over the loan term, meaning you pay more initially. One strategy that makes financial sense for some is to pay points to bring the rate down over the term of the loan. You'll pay more initially, but you will come out ahead in the long run.
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