When you're promised a "rate lock" from your lender, it means that you are guaranteed to get a set interest rate for a certain number of days for your application process. This prevents you from working through your entire application process and finding out at the end that the interest rate has gotten higher.
Rate lock periods can vary in length, between 15 to 60 days, with the longer ones typically costing more. You can get a longer period for your lock, but in doing so, will likely have a higher interest rate than you would have with a shorter period
In addition to going with the shorter lock period, there are more ways you can get the best rate. The more the down payment, the lower your rate will be, as you will have more equity from the start. You could choose to pay points to bring down your rate over the term of the loan, meaning you pay more initially. To a lot of people, this is a good option..
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