Most of the utility trucks that get a refurb come out with their hoses and belts painted too. They are work trucks, not show trucks.. The paint just wears off on the belts, it's not like they are sitting in a bowl of liquid getting saturated and rotting.. They last for years with no issues so I'm not sure what's so horrible about it.
It's a pretty quick paint job, but if it all works with no crazy noises then it's probably fine. Any heavy rust, pitting or leaks should be fairly easy to spot. He obviously did not put too much effort into making it a show piece, but then again he did put some effort into making it look decent. ( I might have picked another color) I say it's probably fine.. The gauge and regulator look clean to me. If he's taking broken equipment, then it only makes sense that he knows what he's doing since he's obviously fixing them to sell or use..
Chances are its a good running unit that looked tired, so he just wanted it a little more presentable to sell. Now It's clean and not all banged up looking.. You're in a forum full of critics so don't expect anyone to call it a masterpiece. If you want a compressor that size and it's in your price range I would check it out. I think people are over reacting..