Thinking of taking on a mortgage from a family member? Then you'll likely look into a mortgage assumption agreement.In real estate transactions, an assumption agreement allows a third party to "assume" or take over the loan of the property's seller. An assumption clause in a mortgage contract allows a home's seller to pass responsibility for the existing mortgage to the new homebuyer. If you think you need an assumption due to a death or divorce, read this guide to learn how to work with your lender and get what you need. This agreement must outline that one spouse will assume the mortgage and take full responsibility for future payments. Loan assumption acquisitions present a unique opportunity for investors, provided they negotiate specific terms into the purchase and sale agreement.