When you're promised a "rate lock" from your lender, it means that you are guaranteed to get a certain interest rate for a determined period for the application process. This protects you from going through your entire application process and finding out at the end that your interest rate has gotten higher.
Rate lock periods can be various lengths of time, between 15 to 60 days, with the longer spans typically costing more. The lending institution can agree to lock in an interest rate and points for a longer span of time, like sixty days, but in exchange, the rate (and sometimes points) will be higher than with a rate lock of fewer days.
In addition to choosing a shorter rate lock period, there are more ways you can get the best rate. A larger down payment will result in a lower interest rate, because you're starting out with more equity. You could opt to pay points to improve your rate for the loan term, meaning you pay more up front. One strategy that makes financial sense for many people is to pay points to reduce the rate over the term of the loan. You'll pay more up front, but you will come out ahead in the end.
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