You have a consensus already --- but he got hosed...at any price...
Its a lesson for you and your buddy ...you need to educate yourselves before you buy any weapon. Its better to lose out on a good opportunity / if you don't know anything about the gun ...than end up with something that is useless ...and then you'll be prepared to make a better decision next time you run into the same gun for sale.
I hate to see anyone get taken advantage of / but unfortunately I think it happens a lot in the used gun market.