Z,
Welcome, glad to have you aboard. I think that the best method for determining fair market value is to chart recent sales. Where do you find recent sales: ask sellers and brokers. You would be surprised at how much info you can get just by asking.
Brokers (who want to stay in business) will tell you truthfully what a coach is worth. Remember they want to SELL; compare their quotes with their competition - this just keeps them honest. We have some great, knowledgeable brokers as sponsors on this POG site. Give them a call - they can help a lot.
Like Reagan said, don't be afraid to make a low offer - you may be pleasantly surprised. A seller who believes in his coach knows what it is worth and he shouldn't be offended when you make a low offer. He can politely decline the offer or make a counter-offer. If you love the coach and it has everything you like including colors it may be worth a little more than fair market value.
A few posts back, someone mentioned tire life and battery life. Rear tires should be replaced every 5 years and front tires should be replaced every 3 years, regardless of tread wear. Start batteries should be replaced every 3 years and house batteries every 5 years. These are averages, just a yardstick for you to have something to guage by.
One more thing: try not to let the seller see you grinning from ear to ear when you step inside the bus. It's a dead give-away!
Good Luck and happy bus hunting. Look forward to meeting you one day.
Tuga & Karen Gaidry
2012 Honda Pilot