You have absolutely NO recourse. Possibly some if you pay via credit card or PayPal but otherwise, none. I bought a set of NHT 3.3's via Craigslist this past November BUT I drove to the seller's locations, WITH A FRIEND, and paid cash on the spot.
It's likely that the deal you're looking at is okay and the seller is a straight-up guy but look for red flags. If the deal's too good to be true, there's your first red flag. Remember that there's ALWAYS another deal in the future.