I've never bought/sold a gun from a private party, but this would seem like a good time to take a friend. I think I'd have a friend just stand away from the transaction and silently observe. Of course, given this modern age, would anyone think it out-of-line to have the friend make a video recording of the meeting using a smartphone or other video recording device?
Make the deal in advance, pending inspection. Then the negotiation part is over. If the item's not as stated (NEVER happened to me - but in case...) then do the deal or don't do it, as you wish.
I frequently meet for Private FTF sales / trades at my local Gander Mountain parking lot. Bought and traded more guns in their parking lot than from inside the store.
I don't see any harm in bringing a friend. I have done this with one of my buddies. We always meet in a well traveled, public place. As others have said, INGO buyer/seller is better than armslist buyer/seller in my opinion. If I don't know someone I will check their profile here, their Facebook and LinkedIn account. I want to know as much as possible. I like to do a simple bill of sale with our names, cities and gun serial number. Just to be on the safe side.