It seems to be a fair price to me. It will be a bit small to spray paint if you use the older style spray guns like I have. I'm not sure how much is needed for the HVLP guns that are available now.
It’ll run hvlp just fine or at least mine does and I think I have the same model. Wouldn’t go any smaller tho.
It’s 220v as you mentioned. Many people do not have 220 in their garage so that may be an issue. I’m pretty sure this particular tank did not actually come with a power cord. It is no problem to put a cord/plug on it or hard-wire it in. My guess is a cord and plug would run less than $25 depending on what you get.
Price sounds fair. Keep in mind an auto shop can run a ton of tools off compressed air and the fact that he needs a larger unit confirms that. A non-industrial unit can get worn out pretty quickly with hard use like that so I would be cautious if you plan to keep it long term as it could already be abused.
Price seems fair, it's probably been used hard. Will he let you bring a cord and plug it in at his shop? If you can't test it then u gotta just decide if you trust him