A monthly interest rate can be included on the promissory note. Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment.A promissory note that requires smaller payments early in the term of the loan and a large payment at the end of the loan term. This Michigan promissory note template is designed for monthly installments now. 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.