When you are promised a "rate lock" from the lender, it means that you are guaranteed to keep a particular interest rate for a determined period while you work on your application process. This ensures that your interest rate won't go up during the application process.
Although there might be a choice of rate lock periods (from 15 to 60 days), the longer spans 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 span of time
There are other ways to get a good rate, besides opting for a shorter rate lock period. The bigger the down payment, the lower the interest rate will be, because you will have more equity from the beginning. You might choose to pay points to lower your interest rate over the loan term, meaning you pay more initially. For many people, this makes sense and is a good deal..
Do you have a question regarding a mortgage program?