What are you thinking as far as airbrushing?
There are a LOT of guides online and several airbrushing communities.
Airbrushing will be much more of a niche market than
headlight restoration and the like. Anybody with foggy lights will want them clean once they see the difference. Airbrushing is pretty easy to get into but there is a very limited market for it. And if you're going to do it right, it's not a quick win as most airbrush enamels won't stick will to a glossy clearcoat so you'll be dealing with either:
A- a lot of priming and taping and whatnot with time for curing and multiple coats
or
B- a half-assed job that will come off the next time somebody hits it with a DA/Rotary.
I do a lot of airbrushing but I do it on computer cases and the like. A nice double-action airbrush with a decent compressor can be had for under $200 but those won't do it for large surfaces.