The length of a rate lock for a home can vary depending on the agreement between the lender and the borrower. The more typical time periods are 10, 15, 30, 45 and 60 days.
Rate locks with a shorter time period have lower interest rates but tend to hold more risk, while longer rate locks have higher interest rates but tend to be safer. After the rate expires, the lender could offer an extension of the rate. If an extension is not offered, then the original agreed-upon rate could no longer be available. In this circumstance, the borrower could be paying the current market rate.