Hope you get some recourse on this deal.
I always ask for the Address and phone number, work number of seller, then I google it and see actually what building it is.. if its a drugstore or post office building other than a home it sends red flags to me. I may even call the numbers and verify they are correctly owned by seller. The cost of a call to sellers work place and them never hearing of the guy is cheaper than losing $1000"s of dollars.
I then ask for a pic of his drivers licence in front of the item for sale to ensure he actually has that item or not and that his name and previously stated address are on the drivers licence. Refusal sends a red flag and I move on.
I ask for serial number of item for sale and run it by the Manufacturer for any mods, repairs, updates and if any, to whom this item belonged to and push for any info they are willing to share.
I google sellers name and if he is legit and its the correct name he may come out as an honest guy selling his gear or if he's a scammer, the numerous forums on the net may have his name connected to previous scams.
One can never be too trustworthy of internet deals as total anonymity and great distances make a scammer brave enough to rip people off.
I can t afford such a loss and Buyer do your due diligence to make you comfortable completing an internet transaction.