It's hard to judge a car by just pictures alone, you'd really have to be there and get a feel for it. How does the tranny shift? Has it ever been replaced? Any rattles? Tires look new, but they look like el cheapo brand. Is it a car that had the jet kit recall, or did it have it from the factory? Does it have more CarFax info (leased, fleet, what region did it come from, etc)? I have one friend with an 02 (same drivetrain as the one you listed) that had the tranny go out. Another one, 04 Ody, had one of the valves (EGR, PCV, one of those) go out and cause tranny problem too.
$18,000 is a bit more than I'd pay for an Ody like that, but that's just me...I never go by market value, just what I feel the car is worth. I think $16,800 is a bit closer to fair market value. Consider that I found a 2000 Ody EX NAV the other day with 46K on it for $9500...I thought that was a blazing good deal. Not certified, and doesn't have the awesome 240HP/5AT combo, but for the price difference and considering it has better equipment, I think I could live with replacing a tranny and a few less HP Just food for thought. In the end, if they like the car and they're willing to pay for it, then take it and enjoy it