balloon addendum
n.— «The friend asked her if she was aware of something called a “balloon addendum.” The addendum states that in 40 years, when she is in her 80s, she will have to make one payment for the entire remaining balance, which will by then be $98,000.» —“Slimy loan hits home” by Diane Valden Independent (Columbia, New York) Oct. 3, 2008. (source: Double-Tongued Dictionary)