try to find a storage unit with climate control, lighting, and electrical outlets (if you have to power your PA, amps, laptops for midi or whatever, and lighting, there probably won't be enough juice for all of that...that's why it might be best to have a place with lighting inside the actual unit). keep in mind, quality storage units are walled in with concrete, with a metal garage-style door, so you'll want to get some carpets on the floor, and some fabric on the walls to keep the echoing under control. me and my old bandmates did this. i went to a flooring place, told them what i was up to, and they were eager to give me some unwanted carpet (not much was wrong with it, no chemicals spilt on it or blood-lol, the weaving was a little screwed up, and some dark spots from the factory.. held together fine, just couldn't be sold). i tipped the guys that helped me pack it up, since they don't do that usually, and i had a shit ton of sound absorbing material for next to nothing!!! we placed a big sheet of it on the floor, then cut the rest into smaller squares for easier handling. what we cut was glued onto the walls with a hot glue gun (i made a large X on the back of the carpet and a split second later another dude would slap it onto the wall). just use a chisel to get the dried glue off the wall when you're done!!!