Check the Seller’s Profile
Marketplace allows you to send a message to an individual on Facebook who is not in your personal contacts without it going to a slush message folder. Once you have found a vehicle that you’re interested in, you can send a message and check the profile of the seller.
Depending on the seller’s privacy settings, you should be able to get a good idea about the seller based on their public Facebook profile. This is no different than doing a Google search on an individual who you anticipate doing some sort of business with. If the profile seems legitimate, you can proceed with organizing a showing.
If the profile doesn’t have any pictures of the individual, or it was only recently created, you might be looking at a fake profile. Also, if the seller refuses to give you a phone number or other contact information, you might have discovered a scam and it is best to block the user.