I have 2 full size 48U cabinets, in my house.. yes, you'd think i have alot of space.. but one cabinet is packed full and the other is my wiring closet and its well allocated.. I just cleaned out dozens of old servers that I am going to haul off to the recycler soon.
never put em in a garage.. not only will you melt em all down you'll fill all your gear with dust and debris, plus they hate to run on the same circuitry as heavy equipment.. I seen welders fuckup phones and ipods, would hate to see what it'd do to a NVR.. and stuff like fluorescent lights and electrical motors of any sort are just electrical noise generators.
A warehouse or large shop, perhaps.. if its adequately ventilated and you can dedicate a circuit to it, but your going to want to mount it high so nobody ever smacks stuff into it, and then need go up there with the air compressor regularly and blow out the dust before it builds up too bad.. and fill it with components tolerant of a lil abuse, a power conditioner would be wise.
my server room is a hot one, I have no aircon.. it was put in basement so it'd be easier to cool, I built my servers with extra cooling capacity (water) and go through great efforts to keep air circulating evenly through everything.. still the server room only tops out in the high 80's in for a few days in the summer and the exhaust coming out is removed entirely from the house, my basement used to have a fireplace.. i exhaust it out the old flu.. if the fans shutdown even for a little while things get bad fast on a hot day.