Mortgage Sale Transparency Act of 2017 This bill amends the Truth in Lending Act to require in the event of a mortgage loan sale, transfer, or assignment to another creditor: (1) notice of the transfer to the borrower from the original creditor, (2) exemption from liability for the borrower in the event of an error in the transfer, and (3) a 90-day grace period for loan payments made by the borrower to the wrong lender.