A few things I do when contemplating FBM ads. Check how long the seller has been a member of FB. Same year as ad, avoid. Click on sellers other items for sale. Sometimes the same vehicle will be for sale in a dozen or more markets and it's always a too good to be true deal. Two big red flags. On their FB profile, no friends, or just a couple sketchy pics. Again, just not right.
Lots of sketchy folks trying to steal money in Marketplace. It's always buyer beware.