When you are offered a "rate lock" from your lender, it means that you are guaranteed to get a certain interest rate over a determined period for your application process. This prevents you from working through your entire application process and learning at the end that the interest rate has gotten higher.
Although there are various lengths of rate lock periods (from 15 to 60 days), the extended spans are usually more expensive. You can get a longer period for your lock, but in choosing this option, will likely have a higher rate than you would with a shorter rate lock span of time
In addition to choosing a shorter lock period, there are other ways you can attain the best rate. A bigger down payment will get you a lower interest rate, since you'll be starting out with a good deal of equity. You can pay points to lower your interest rate over the term of the loan, meaning you pay more initially. For many people, this makes financial sense..
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