When you're offered a "rate lock" from the lender, it means that you are guaranteed to get a specific interest rate over a certain number of days for your application process. This means your interest rate cannot grow as you are working through the application process.
Although there are several lengths of rate lock periods (from 15 to 60 days), the longer ones are typically more expensive. You can get a longer period for your lock, but in making this choice, will probably have a higher interest rate than you would with a shorter period
There are more ways to get a low rate, in addition to agreeing to a shorter rate lock period. The more the down payment, the smaller your interest rate will be, as you will be starting with more equity. You could choose to pay points to improve your interest rate for the loan term, meaning you pay more initially. One strategy that is a good option for many people is to pay points to improve the rate over the life of the loan. You'll pay more up front, but you'll save money, especially if you don't refinance early.
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