Side hustles

Any of you guys teach yourself how to do something on the side, aside from fixing cars?

I’m at the point in my career that I don’t really want to fix cars at home anymore, aside from easy stuff like brakes etc. I make a decent living doing it at work but extra money for home projects never hurts especially with the current cost of living. I’m talking like detailing and more specifically tinting windows.

I’ve never attempted to tint windows before, but im going to try and practice on a couple of the cars I do have at home with good quality 3m tint (one is a sedan, the other is a hatchback) It just seems like easy money once the skill develops enough that I’d be confident to do it on someone else’s vehicle.