Buying an iPhone off fbmarketplace

Yes he can and buying a phone off FB Marketplace is one of the most scam ridden ways to buy a used iPhone. Offer Up, FB Marketplace and eBay should be avoided like the plague, unless you can afford to lose whatever the cost of the phone is.

Read this --> The All Too Common SAD Reality of Buying … - Apple Community

Is there any chance that seller after selling me this phone, he can report it as stolen to Apple and they could then possibly lock my phone and give him a new phone?

There is a chance that after selling you the phone, the seller can report it as stolen to his insurance company or carrier to have the phone "blacklisted", meaning that the phone will not be usable going forward.

The seller gets a new replacement phone and he also has the money for the phone which he sold to you....and you have a useless phone. This is a common scam.

Only consider buying a used phone from someone that you already personally know to be honest.

Otherwise, it is a roll of the dice.

By buying used Apple products from third party sites, you are assuming the risks that it can come Activation Locked and practically useless.

Read about the risks and reality of buying used Apple products by our very own lobsterghost1! ⇢

The All Too Common SAD Reality of Buying … - Apple Community

-Zachyy ✌️

You would think that FB would protect their users from the scams that other FB users post on their site, but that is not the case. The only thing they offer is to Report a Seller, which does absolutely nothing. They are not going to give you your money back if you get scammed. That is a huge gamble that you would be taking and having to put your trust in an anonymous seller that you do not know. Yes they are free to scam you and there would be nothing you could do about it. Don't do it.

Adding on, you should really only ever buy your Apple products from Apple or an Apple Authorized Retailer to be safe from these.