When you're offered a "rate lock" from a lender, it means that you are guaranteed to keep a specific interest rate for a determined period for your application process. This saves you from going through your entire application process and learning at the end that the interest rate has gotten higher.
Rate lock periods can be various lengths of time, anywhere from fifteen to sixty days, with the longer period generally costing more. A lender may agree to freeze an interest rate and points for a longer period, 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 more ways to get a better rate, besides agreeing to a shorter rate lock period. The more the down payment, the better your rate will be, since you will have more equity from the start. You can pay points to reduce your rate for the term of the loan, meaning you pay more initially. To a lot of people, this makes financial sense..
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