When you are offered a "rate lock" from the lender, it means that you are guaranteed to get a set interest rate for a certain number of days while you work on the application process. This ensures that your interest rate won't rise 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 doing so, will most likely have a higher rate than you would have with a shorter rate lock period
There are more ways to get a better rate, in addition to opting for a shorter rate lock period. A bigger down payment will give you a better interest rate, since you're starting out with a good deal of equity. You could choose to pay points to bring down your interest rate over the life of the loan, meaning you pay more up front. One strategy that is a good option for some is to pay points to improve the interest rate over the life of the loan. You are paying more initially, but you will come out ahead, especially if you don't refinance early.
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