Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. The borrower makes monthly payments of interest only, and then pays off the entire principal in one lump sum.You can use this form for up to four borrowers. An unsecured promissory note with a balloon payment can be a great way to obtain financing for your business. The note doesn't require collateral. A Promissory Note with Balloon Payments is a loan contract that enables a lender set loan terms with one or more larger payments at the end.