And the reason you would have to charge $50 per hour is to cover the liability insurance.
WRONG...Never even considered it. Sorry..but spend some time and do the Math...
A simple 10 bay garage in the Boston (outside of the 495 belt) area can easily run you 10-20k PER month...If in Cambridge...try $40k/mo.
Those lifts aren't cheap...Not to mention heating/water/damage...and there are LOTS of things I'm NOT including...Insurance is NOT of of them.
I do know a guy in NH that does it. He's a mechanic with a 5 bay garage...He'll rent out 1-2 of the bays from time to time. But 90% of his income come from his business.