That's a very thorough answer Zwielicht!
My recommendation would be- if you are relatively new to affiliate marketing/IM in general, I would not think about a private affiliate network...unless you have some very good contacts with strong advertisers.
Your main problems would be 1. where will you find affiliates? and 2. how will you get affiliates to trust your network, when they can promote similar products on well-established, reputable networks?
Mancar