about if they give you access to a gym? Do you pay tithing on use of that gym? How about when they pay for your flight and hotel in connection with your job (how is that different than you paying for things so you can do your job?)? How about when they take you to dinner or provide you with a shirt?

Tithing can be complicated when you start to break things down.

I can see an approach that money you spend to stay alive (I.e., food and shelter) and support your efforts to earn money (i.e. gas and vehicle expenses, work clothes, licensing fees etc.) are not an increase rather they are necessary expenses.