When you're promised a "rate lock" from your lender, it means that you are guaranteed to get a specific interest rate for a determined period for the application process. This keeps you from working through your entire application process and discovering at the end that your interest rate has risen higher.
While there are various lengths of rate lock periods (from 15 to 60 days), the longer ones are usually more expensive. You can get a longer period for your lock, but in doing so, will most likely have a higher interest rate than you would have with a shorter period
There are other ways to get a reduced rate, in addition to opting for a shorter rate lock period. A larger down payment will result in a better interest rate, since you will have a good amount of equity at the start. You can pay points to improve your rate for 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'll pay more initially, but you will come out ahead in the long run.
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