It sounds like you are speaking of assuming the loan. There are certain loans under certain conditions where you can assume the loan and interest rate of the existing mortgage. If you are able to do so you will have to qualify for the loan just as if you were getting a new loan. Depending on how long the existing mortgage has been in existence it could be a higher interest loan than what you could get on your own. A good lender could explain this when you go in for pre-qualification. Let me know if you need help with a home purchase.