My place has no master valves in the bathroom branch for the cold water feed. I can shut off the hot water though since that comes from an on demand unit that I

My place has no master valves in the bathroom branch for the cold water feed. I can shut off the hot water though since that comes from an on demand unit that I installed. I have to shut off the entire condo building (14 units) to do any work in there. You can be sure that I'm going to add a master valve to that branch...