Following up on something I mentioned in passing, and that I thought about after my post, and which I see Jim mentioned.
Crucial is the quality of the work. The work of the entire co-op will be judged as being as good as the least fine of the work. So it all better be top notch. As Jim said, no one should be accepted merely because they can help pay the bills. If I saw the listings of a co-op and a few people in it did sub-standard work, I would not pursue any part of it. That may be just me, but I don't think so. I assure you that all serious collectors will feel the same. The only sales that would be made otherwise would be the very occasional one if someone falls in love with a print--and that kind of sale only happens at very low prices.
If the object of the co-op is to sell prints, you all have a lot of work ahead of you. If you are going to be successful, consider that you will have a new full-time job. Putting less time into it is a waste of time and will lead virtually nowhere.
This sounds harsh, even to me, but my recommendation is to go into this with your eyes wide open with no illusions. And really, do be prepared for 40-hour weeks on this if it is to amount to anything.