IMO, if buying used, try to buy in person but I've had good success buying used wheelsets on Ebay. I look at the feedback of the seller and look closely at the pics. I ask as many questions as I can about the history and i go with my gut. I bought a set of Boyd 38 carbon and a set of Boyd Vitesse alloy wheels and they both came out just fine. Saved a bunch of money that i used to buy other stuff.