Affiliate Marketing Secrets

I have a great deal of knowledge on holistic healing, and know of some of the topic supplement companies in the industry who have a lot of integrity and provide excellent health benefits and improvements. I want to affiliate myself with several of them, and direct traffic toward my propsed site to begin gnerating income to live with.
The friend who offered to make the site is an IT computer programmer. He deals with top clients in New York and seems to really know what he is doing on the Net. He has a degree in it.
He has asked me to write 50 pages of material educating people on health. I love to communicate, so it will be fun to do and get all my thoughts out there to help people better manage all their illnesses. After I do this, we will look at adding various companies to the stie to direct people to high quality products.
He knows how to deal with the legal end of things, like disclaimers etc….if anyone tries to sue us for anything. He is going to send me a contract for us to work together.
WHat I was wondering about is a scenario where once he has everything up and running, if Im doing all the work after that, trying to direct people to the site, offering them technical support by answering their questions etc…..is it fair that he gets 50 % of all the income that comes in ?
I have never signed a contract like this. I don’t want to be greedy or ungreatful, yet I dont want to be taken advantage of either. Is it normal that once someone sets up a site for someone, and the other person is doing all the work to deal with the clients, that the computer guy who set it up gets 50 % of all the profits ?
Any suggestions in what things I should look for or what things I should ask for in such an agreement, and if 50 % is a good deal since i dont know anything about how to manage a site ?