I currently share a studio with five other photographers. Half of us are paid and half are hobbyists. From the beginning we made sure everyone's name was on the lease so no one could back out of it easily. From that standpoint, it's worked very well. We set up a calendar on Google Calendar and everyone uses it to schedule their shoots on a first come first served basis. There are two things that developed as "problems" for us. One, during the Winter months when everyone wants/needs to be in the studio, we had one partner who would only schedule time once a month, but he would schedule it for 7-8 hours on a weekend, and it was always from 10 am to 5 pm; prime time! This prevented those of us who had paid gigs from accessing the studio during that time. We finally had to implement a weekend only schedule of 8-noon, noon-4pm, and 4pm to whenever. This allowed 3 of us to shoot on any given weekend. The other major issue is that 95% of the work, clean up etc. was performed by three of us with the others reaping the benefits. The three of us are now seeking our studio. So, my advice to you is pick your partners carefully and make sure you have ALL of these things in writing ahead of time so everyone is on the same page. Good luck!