How to make a zero interest rate note sizzle!

[Mike Mitchell]

I have found a note with a upb of 28,500, zero % interest, with 114 payments of $250 remaining. A note at zero % interest is unenforceable in Texas and the note cannot be purchased as it is. I offered $13,636.35 which results in an 18% yield, but the seller knows that the note cannot be sold until we revise it to everyone's satisfaction. If I "lower" the upb and put in the minimum required interest rate of 1.5%, the mortgagor will still pay $28,500, but I would be hurt if they refinance or pay off early.

If I could convince the mortgagor to raise the payment from $250 to $350, and take $500 off of the total amount which will be paid over time, I would raise my yield to 24%.

The big question is how can I prevent an early payoff at the upb which will show on the amortization chart?

Any other ideas on how to "fix" a zero % interest rate note.