Thanks everyone, so several liability seems to be the key.
To answer some of the questions people had about my situation.
1. The four people all want to move into the condo. It's a 2 bedroom so they should all fit. 2. We are still doing the due dilligence and it's coming out well. They make enough collectively, and one of the four would be able to afford the place by himself. Each couple by themselves would also be able to afford the place. All four credit are good and good history with landords. employment seems to be in order for all four of them. 3. Our biggest apprehension is with the arrangement itself. We were accustomed to renting to a single family. Reading on topic like these, there are a lot comments on the web about the inevitability of couples breaking up and the mess that ensues. I think we know enough now not that we are getting more comfortable with being able to handle the situation.
Have a plan in place should the cohabitation not work out and a couple either breaks up or a couple decides to leave. How would you handle replacement? In Pro Tenant California it can get sticky...so school yourself here and on the States Consumer Affairs site.