When you are offered a "rate lock" from the lender, it means that you are guaranteed to get a specific interest rate over a determined period while you work on the application process. This means your interest rate can't grow during the application process.
Rate lock periods can be various lengths of time, anywhere from fifteen to sixty days, with the longer spans generally costing more. You can get a longer period for your lock, but in choosing this option, will probably have a higher interest rate than you would with a shorter rate lock period
There are other ways to get a reduced rate, in addition to choosing a shorter rate lock period. A larger down payment will give you a lower interest rate, because you are starting out with a good deal of equity. You might choose to pay points to reduce your interest rate for the loan term, meaning you pay more initially. One strategy that is a good option for some is to pay points to bring the rate down over the term of the loan. You'll pay more initially, but you will save money in the end.
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