Here's the information you'll need to have handy to complete your unsecured promissory note, interest-only with balloon final payment. Here's the information you'll need to have handy to complete your secured promissory note, interest-only with balloon final payment.Interest Only Payments. Start calculating now. The loan is now spread out over 34 yrs. A single final balloon payment for the entire outstanding Principal amount and interest accrued will be paid on or before the day of. Most consumers with a balloon note refinance their loan before the final balloon payment becomes due.