Carried a 62k note with no amortization schedule, then lost the payoff argument
Sold a small two bedroom house I'd owned outright. 62,000 note, 8%, twenty year amortization with a ten year balloon, payment worked out to about 519 and we rounded it to 520. Attorney drew the note and the deed of trust, it got recorded properly, all of that was fine.
What I did not do was set up any way of tracking the loan. No servicer, no statements, no amortization schedule attached as an exhibit. Payments came by bank transfer and I wrote the date and the amount in a notebook. Some months the buyer sent 700 or 800 instead of 520. I deposited it and thought nice, he's ahead.
Month 26 he got approved at a credit union and asked me for a payoff figure. I built a schedule after the fact and came up with 59,800. He came back with his own spreadsheet at 55,100, because he'd treated every dollar over 520 as principal from the day it landed and I'd been treating some of it as prepaid next month. We were 4,700 apart on a 62k loan.
My attorney's view was that the note didn't clearly say how prepayments applied and that gap was mine. We settled at 56,400 and I paid 1,600 in legal on top. Call it 5,000 total.
Also learned that accepting eight late payments without ever sending a notice made the late fees uncollectible in practice, so I never saw a dollar of those either.
What I'd do differently: schedule signed as an exhibit to the note, one clear sentence on how extra money applies, and a statement to the buyer every month even if I'm the one typing it.