I bought mine off eBay and flew down from KC to TX to pick it up. The listing included dozens of pictures along with a clean Carfax report. I brought along an OBD-II code reader and a bunny suit (tyvek jumpsuit not a bunny costume
) to do my own inspection.
The listing required paying a deposit via Paypal and bringing guaranteed funds. I didn't present the payment until I throughly inspected everything.
One final layer of protection was the free warranty Square Trade provided me (3 months / 3k miles I think it was) with the option to convert it to a longer term.
Based upon the seller's feedback and sales volume, the price research I'd done, and the back-up protection of the warranty, I hit the BIN and never regretted it.
To date the only problems I've had were the rear air bags leaking after a few months and the ignition/start switch I replaced myself for $38 bucks.