Is this sale on twitter legit or is he trying to scam me?

I messaged a guy on twitter about iphones he says hes selling. He seemed legit until he said that I had to pay with a vanilla card. I don't understand if this is secure or not. He claims that there's two serial numbers and if i give him one than he will get verification of the payment or something. It sounds to me as if its a scam. Can someone please let me know your thoughts. Also heres a link to my convo.

You can NEVER get a refund from a Vanilla card which is why scammers ask for them. You NEVER buy any phone unless you either buy directly from an Apple store or phone store, OR you can meet the seller in person at the phone store where he has his contract to transfer it to your name right there -- so he can't claim it was stolen later and get it deactivated
With a Vanilla card you won't get anything and can't get your money back. Otherwise it will be a cheap Chinese fake that might look like an iPhone but will not work with the App Store meaning you can't use any apps. Or it will be stolen or reported stolen after you buy it so he can get a new phone from his insurance company