We know. You want those sneakers and you want them RIGHT NOW. They sold out at your local Foot Locker/Niketown/mom and pop store, and waiting is not an option. Well, hold up a second there, champ. Before you click on "Buy It Now," take a gander at A Guide to Buying Sneakers on eBay, and keep some of that hard-earned loot in your PayPal account for the next pair.