Assumption of Loan Requirement Letter for disaster loan servicing action request packages. About this document and download.What Is Required to Assume an SBA 504 Loan? An assumable mortgage involves one borrower taking over, or assuming, another borrower's existing home loan. Find out how it works. Loan assumption is when you take over full responsibility of the mortgage loan. Complete the assumption agreement: Fill out and sign the loan assumption agreement, which legally transfers the mortgage responsibility to you. AssumeList is a unique real estate tool that allows prospective homebuyers, investors, and agents the ability to find homes for sale with an assumable mortgage. An assumable mortgage is one that allows a different party to take over the alreadyexisting loan obligations a previous homeowner.