We ran a not-for profit co-op studio a few years ago, it became a real headache because of the book keeping that had to be done, esentually what your doing is combining several different business, which in our state required a full time book keeper to keep track of income and expendutares, we have since converted to a studio that rents out space on a first come first served basis, this had really simplified the record keeping, we provide quite a bit of equipment as part of the rental, which the rule in place that anything that is broke or destroyed by a renter is replaced by them, when we had the co-op, we also had to maintain a insurance bond on the property and the co-op that we don't have to do any longer, we just maintain a liability policy on the property now, and the individual photographers that rent space are responsible for their own insurance, and believe me insurance is expensive and needed, one of the photographers that was part of our co-op decided he was going to take money for shooting and did not deliver the product, so they sued the co-op and not the photographer, which really turned out to be a mess.

There is alot of things to take into consideration when doing a venture of this nature, it is alway a good idea to talk to a business adviser as well as an accountant, so they can explain the tax and business implications of the various types of set ups.

If I can help further, don't hesitate to let me know, I have been there!