When you are promised a "rate lock" from your lender, it means that you are guaranteed to get a particular interest rate over a determined period while you work on your application process. This ensures that your interest rate won't grow during the application process.
While there are several lengths of rate lock periods (from 15 to 60 days), the longer spans are typically more expensive. You can get a longer period for your lock, but in choosing this option, will most likely have a higher rate than you would have with a shorter rate lock span of time
There are more ways to get a low rate, besides agreeing to a shorter rate lock period. A bigger down payment will give you a better interest rate, because you're starting out with more equity. You could choose to pay points to reduce your rate over the life of the loan, meaning you pay more up front. To a lot of people, this makes sense and is a good deal..
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