Alan McCraney
The method of amoritization that you are describing (fixed principle payments, declining interest) benefits you as the seller by allowing you to pay-down principle much faster than a normal mortgage amoritized under standard fixed payment method. It looks like he is offering you a 15 year mortgage.
By my napkin math, you'll pay $44,094 in interest with this gentleman's repayment schedule and $51,894 with a normally amoritized mortgage...a savings of $7800 over the life of the note. But...something to consider....your initial monthly payment will be higher under his method ($1055 versus $843). The cross-over point will be in month 74 (a little over six years).
So....do you want higher cash-flow up front with a lower monthly payment, or do you want to pay less interest over the life of the loan? For me, cash flow is key.
By the way, I agree with Bill Gulley - 6% isn't bad for seller financing (with nothing down it appears from your note).