I have been doing this for several years, but we don't call it a co-op. We call it a freindship. I to have the same problem with my circle of freinds(them not being as serious as I am) however I use that against them in a positive way by motivating them to take this sport of hunting to their next level. I'm not bragging but I almost always bag more or bigger animals then they do and always encourage them to take the necessary steps to do the same.
We are all underfunded when it comes to buying what we need or think we need so sharing expenses with freinds is very smart.