I wouldn't do it without a well-reviewed eBay account or some other system with some form of security.
Think about it...why would he randomly PM YOU with the offer (unless you've requested such a system at some point)...that's the thing with online scams. People who fall for them never wonder why out of all people to make the offer to THEM? Why email the great offer to someone randomly they don't even know? My point is, be careful.
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