That’s why we went straight to the experts to find out what you need to know if you’re thinking about refinancing. You could find extra cash by refinancing your mortgage. The cost of so-called “free” refinancing will be added on to your interest rate. Let’s say you need to refinance $250,000 with a 3.5% interest rate, you will save more than $1,100 a month (assuming your current interest rate is 5%). But before you call a lender, it’s important to know why you’re refinancing.