Upload & Sell: On
I've never dealt with a situation like the one you've described, but there have been other members who have posted about similar situations. It seems that a lot of the input given to those members - and what I'd tend to advise myself - is that you should "go with your gut." If you are uncomfortable for any reason, simply decline the sale. It is your right to sell to whomever you would like to. I'm sure you will find another buyer. I wouldn't want to rush to judgment and say that this individual is trying to scam you, but if you have your doubts, then why proceed? Nobody is in a better position to make that call than you.
Best of luck with your decision and sale!