When you are offered a "rate lock" from a lender, it means that you are guaranteed to keep a specific interest rate for a certain number of days for the application process. This ensures that your interest rate won't rise during the application process.
Rate lock periods can vary in length, anywhere from 15 to 60 days, with the longer period generally costing more. The lending institution can agree to hold 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 a shorter period.
There are more ways to get a good rate, in addition to opting for a shorter rate lock period. The bigger down payment you make, the lower your interest rate will be, because you will have more equity from the start. You may opt to pay points to reduce your rate for the loan term, meaning you pay more initially. For many people, this makes financial sense..
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