When you're offered a "rate lock" from a lender, it means that you are guaranteed to keep a set interest rate over a determined period for the application process. This prevents you from getting through your whole application process and finding out at the end that the interest rate has gone up.
Rate lock periods can vary in length, anywhere from fifteen to sixty days, with the longer period generally costing more. A 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 going with the shorter lock period, there are several ways you are able to score the lowest rate. The larger the down payment, the better the interest rate will be, because you will have more equity from the start. You could opt to pay points to bring down your rate for the loan term, meaning you pay more up front. One strategy that makes financial sense for some is to pay points to reduce the interest rate over the life of the loan. You are paying more initially, but you will come out ahead, especially if you keep the loan for the full term.
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