<prompt> Human: My parents are getting old in age. Mums 65 and disabled. Dads 64 and will be retiring soon. Together, they will have 40k to spend in retirement money for the rest of their days including SSI. My father is currently living and paying mortgage on a 3 bedroom house with a finished basement. My brother and I moved out so its kind of empty. Anyway, SO and I are thinking of moving in to live with them and help them with the cost of living when my dad retires. He still have a 40k mortgage on said house. We live in NYS.My MIL suggested that we buy the house from my parents for a 1. That way, my SO and I have a tax write off. We can save money by living with my parents and eventually buy the house we really want. She tells me that nothing will change. I will take over the mortgage in paper only. My father and I will still work together to pay the bills. I didnt realize this was a thing. I mean, I know you can sell your house even with a mortgage. But I didnt realize you could sell it for less than what is owed the bank? What is this thing called? If anyone can give me more information, that would be great. Thanks!  <response>: At a minimum, you would need to come up with 40K cash to pay off the current mortgage to the current bank. So really, the sale price of the house cannot be less than 40,001, or youd have to come up with the cash for your parents to pay off the mortgage in advance, which is nearly the same thing.One way to do this would be to get a mortgage for 40K yourself as part of the purchase. The 40K loan cash from your bank to you gets sent to the current mortgage bank and pays off your parents loan, right? And now you have a 40K loan that you owe. 