1997 Boxster from private seller or 1999 Boxster from a dealership?

[Overdrive]

I wouldn't base much of anything on squeaky clean carfax reports...check the title and make sure it's not a salvage, and that'll at least tell you that the car is not likely to have ever seen any substantial damage.

My 97 had a few thousand miles less than the one you're looking at, and I think that price is pretty decent if the car is in good shape. You could probably get it for a bit less, especially if you find anything you'll have to immediately put money into (very likely for a 15 year old car). If the seller has a good track of maintenance records that will be a very good reassurance for its upkeep, unlike mine which literally sat in a lot for 5 years barely ever moving.

I'd hold the dealer to these same standards, but the advantage with the dealer is that you may be entitled to a few months of warranty after the purchase to fix any issues you find. In my state any vehicle purchased for over $3,000 gets 60 days of warranty by law, unless you choose to purchase the car "as is" and take your lumps. Find out what your rights are when it comes to a dealer purchase, and see what the dealer is willing to do as far as a warranty if it doesn't come with one.

Check the driver's door jamb for the placard with the build date on it. It's possible that the very late builds from model year 97 had the updates that came from 98 onward that fixed the frame issues that preclude the 97 from using 18 inch wheels. There's no good way of knowing, unfortunately, but it's at least a possibility.