When you are promised a "rate lock" from the lender, it means that you are guaranteed to get a particular interest rate over a certain number of days while you work on the application process. This means your interest rate won't get higher during the application process.
While there are various lengths of rate lock periods (from 15 to 60 days), the extended ones are typically 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 period
In addition to choosing a shorter rate lock period, there are several ways you can score the best rate. The more the down payment, the smaller your interest rate will be, as you will have more equity from the start. You could opt to pay points to bring down your rate for the loan term, meaning you pay more up front. To a lot of people, this is a good option..
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