When you're offered a "rate lock" from your lender, it means that you are guaranteed to keep a specific interest rate over a determined period while you work on the application process. This prevents you from going through your entire application process and learning at the end that the interest rate has risen higher.
Rate lock periods can be various lengths of time, anywhere from fifteen to sixty days, with the longer spans typically costing more. The lending institution can agree to lock in an interest rate and points for a longer period, like sixty days, but in exchange, the rate (and sometimes points) will be more than with a rate lock of fewer days.
There are other ways to get a lower rate, in addition to going with a shorter rate lock period. A bigger down payment will result in a better interest rate, since you're starting out with more equity. You can pay points to reduce your rate over the loan term, meaning you pay more initially. One strategy that makes financial sense for many people is to pay points to bring the rate down over the term of the loan. You pay more up front, but you'll come out ahead in the end.
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