When you are offered a "rate lock" from your lender, it means that you are guaranteed to keep a set interest rate for a certain number of days while you work on the application process. This means your interest rate can't grow during the application process.
While there are several lengths of rate lock periods (from 15 to 60 days), the longer ones are typically more expensive. You can get a longer period for your lock, but in choosing this option, will probably have a higher rate than you would with a shorter period
In addition to choosing a shorter lock period, there are more ways you can attain the best rate. The bigger down payment you make, the better the interest rate will be, since you will be starting with more equity. You can pay points to lower your interest rate over the loan term, meaning you pay more up front. To many people, this is a good option..
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