I'd never keep snakes in garage either: first thing you have to ask/answer is whether or not you are still going to use the garage for your car? and how often you
expect to be opening & closing it for that purpose. It makes a HUGE difference for the conditions in the garage & what creatures you can safely keep.
I did exactly that when I lived in "high* desert" of So. Cal. for many years. *refers to elevation, not mental states.I had a 4+ car garage that I still parked my van
in, but it was so large that the temperatures were more stable than if it had been a more normal-sized garage. I ran a huge "rodent-ranch" in that garage & it worked
fine for rats, mice & Russian dwarf hamsters; all of those do better with cooler temperatures than with heat. In winter I insulated their cages somewhat...but winters
there were mild & short; for summer, I used a down-draft swamp cooler just for the garage- it was on a thermostat (un-common for swamp coolers but worked great)
& I had 4 'up-ducts' installed for the warm smelly air to vent up & out. BTW, that garage was also "finished" as far as walls & ceiling, btw, & you'll need the insulation!
Exactly what modifications you need will depend on exactly what you want to keep & your exact climate. But snakes in a garage? No way I'd do that...they can get
invaded by ants or spiders, either of which can kill your snakes. (can happen in a house too, but far less likely) Pest control is toxic to snakes- I just wouldn't do it.
I agree with security issues that 303_enfield mentioned too. I didn't have that problem, as that house was fenced in (6' chain link) & locked, & patrolled by the pack
of 4 big dogs I had then (2 dobies & 2 shepherd-mixes). No one even made it to my front door, which carried warning signs for "rattlesnakes on duty" (which wasn't
a lie either, lol). I'd never keep snakes in a way that they were "out of sight, out of mind"...not even the rattlesnakes I had then, all shared my living space so I could
easily & always see what was going on at all times. This is both for my pleasure & their health & safety issues...if anything is wrong, I want to see & fix it right away.