I see a future for a new financial product where the existing owner keeps paying the 2.5% motgage but is sells an option where he’s contractually required to se

I see a future for a new financial product where the existing owner keeps paying the 2.5% motgage but is sells an option where he’s contractually required to sell it for the balance of the mortgage and rent the house for the current mortgage payment. In the old days there was a transferable loan, those don’t exist now but you need a new product to extract value out of an artificially low existing mortgage