How to handle an Amway friend

One of my best friends has been trying to get me to join Network 21 in Turkey. He is a good guy, has my best interests at heart, but is a true believer and thus believes that I should join them. I need a way to get out of this without 1) ruining an important friendship and (ideally) 2) getting him to realize that you can sell products without going to seminars, meetings, buying books, etc