I’d stick with Amazon if I were you. All of my Amazon sites only have Amazon affiliate links. If you use Google Adsense display ads on your site, you’re literally taking people away from your site for the sake of just a few cents with these type of ads. If you direct them just to Amazon, then you have a greater chance of earning more money from that click.
The only difference with the offline middleman and affiliate business program is that the online affiliate does not need to get hold of the actual product to earn revenue. He doesn’t need to shell out money to buy the product that he has to sell. All he has to do is create a site that markets the products of the producer. Every time he makes a sale, the producer will take over to send the actual products, receive payments and extend customer support, when necessary. A special web-based script records this process and thus the affiliate is paid for every successful sale he makes.