The only requirements are that you are able to form a legal binding contract with the seller (which you do when you bid) and that you follow through if you are the winning bidder. Just like the seller, buyers can be rated by the sellers so if you do not follow through you are risking a negative rating from the seller which will be viewable by everyone.
Payment choice is selected by the person posting the auction (Cash, Check, MO, Paypal, CC, etc.) as well as the form of delivery. Once we get it completed, it's simplicity of use will be obvious and it's functionality will be praised.
Scott Z.