Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. Interest Only Payments.Here's the information you'll need to have handy to complete your secured promissory note, interest-only with balloon final payment. A straight note is a written document that outlines the terms of a loan agreement between a borrower and a lender. Most consumers with a balloon note refinance their loan before the final balloon payment becomes due. A monthly interest rate can be included on the promissory note.