The link says the listing has now ended, so this is probably a little late.
In my opinion (and that's all it is) when buying 2nd hand equipment I work on a cost of half original plus about 10%, I factor in the cost of replacing wearable parts (nozzles/needles/ bearings/seals etc) quite often the end figure isn't that far off a new one.
with a compressor there is always a danger that it hasn't been properly cared for, has it been run hot for extended periods, did the previous user drain the tank regularly, if not has there been damage caused by the water... …
Compressor I'd probably bite the bullet and buy new, Airbrushes you can get 2nd hand but factor in that you may need a new needle / nozzle. I think many people buy an airbrush and because they're inexperienced it gets a slight knock and damages critical parts, it then doesn't spray correctly and then the user gets annoyed that they're buying parts so soon and then decides they don't need the hassle.