When you are promised a "rate lock" from a lender, it means that you are guaranteed to keep a particular interest rate for a certain number of days while you work on the application process. This keeps you from working through your whole application process and finding out at the end that your interest rate has risen higher.
Rate lock periods can be various lengths of time, anywhere from 15 to 60 days, with the longer ones typically costing more. You can get a longer period for your lock, but in choosing this option, will likely have a higher interest rate than you would with a shorter rate lock span of time
There are more ways to get a better rate, besides opting for a shorter rate lock period. The bigger down payment you can make, the better your rate will be, since you will have more equity from the beginning. You might opt to pay points to lower your interest rate over the life of the loan, meaning you pay more up front. To many people, this is a good option..
Do you have a question regarding a mortgage program?