My opinion, the amount of money that you and your boss would make in a few hours is not hardly worth him letting you tie up the shop.
How much tint can you do in 4 hours and clean up after you're done and what you are able to charge?
Then the environment of a body shop isn't the best as has been stated. I have tinted in paint booths and I didn't like the lighting. I get blinded by the lights on the sides. Tinting you look out from the vehicle more than looking at it like painting so lights are in your face!
I do a semi mobile set up and work out of other shops and I would not dream of giving 50% to the shop. I provide everything except the shop and customer....the most I give the shop is 20%....
Glass shops, detail shops, accessory shops are all great connections to get a bay and customers if they don't offer tinting themselves.