When you are offered a "rate lock" from the 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 get higher while you are going through the application process.
While there can be a choice of rate lock periods (from 15 to 60 days), the longer spans are generally more expensive. You can get a longer period for your lock, but in choosing this option, will most likely have a higher interest rate than you would have with a shorter span of time
There are more ways to get a low rate, besides agreeing to a shorter rate lock period. The bigger the down payment, the better your rate will be, because you will have more equity from the start. You could opt to pay points to improve your interest rate for the life of the loan, meaning you pay more initially. To a lot of people, this makes sense and is a good deal..
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