Lessons learned: Don't overlook the amount of the late-payment fee. My debtors are late every month with their payment, and all I get for my troubles is a lousy $15 fee. That's a nice little bump of $180 every year, but it hardly covers the extra time I spend for bookkeeping. Recalculating the totals every month is a hassle. And $15 per month doesn't "incentivize" them to pay on time.

Insist on a late-payment fee of at least $25, but why stop there? Go for $35 to $50, and you'll see a much-improved on-time payment performance.

The couple who owns my old house still has to make monthly payments for another four-and-a-half years. Seems like forever.

I used to write to them every month to urge them to take out a bank loan to pay off their loan in one lump-sum payment. Would have been nice to get a that $10,000 chunk of change in one check. But now, I've become accustomed to getting that little $210 monthly bump in my checking account. Why not? I can always use the extra cash, and at the end of the year, I've earned $750 in interest payments from them. Profit's a good thing. (Right, Martha?)