Prepayment penalty on Interest-only Seller Financed Note

[Brian L.]

My home purchase was seller financed. I recently extended/refinanced the note with new terms - in the new contract, the note is interest-only there's no prepayment penalty after 3 yrs but there's also no detail/language in the contract of what that prepayment penalty would be. It's been a little over a year and I'd like to refinance the interest-only note with a traditional 30yr mortgage at a lower rate. What do I do about the prepayment penalty? How do I figure out how it will be calculated?