Most of the (gigging) bands I know personally around here in Houston rent some kind of jam room...rooms specifically for that purpose. While you might have bands playing all up and down the hallway from you, the rooms are generally soundproofed with foam, insulation, and whatnot. Nothing fancy for sure...just a square room with outlets. They keep the heavy gear there and have a key for the door. They average about $150-300 a month. It's either that, or cram yourself into one of the bandmates' houses.