Assumption of Loan Requirement Letter for disaster loan servicing action request packages. About this document and download.Create an account in the MySBA Loan Portal (lending.sba. Gov) to monitor your loan status or to make payments. An assumable mortgage involves one borrower taking over, or assuming, another borrower's existing home loan. Find out how it works. What Is Required to Assume an SBA 504 Loan? When you assume a mortgage from a home seller, you become responsible for that loan at its existing interest rate and terms. I know most conventional loans aren't assumable but there's still possibilities. Just curious on anyone's experiences.