Sold a product but he sent me an invoice as a confirmation?

[jl8545]

Hello,

I sold a gaming account yesterday, and usually when I do I receive the payment straight away.
but yesterday I found something suspicious as the buyer sent me an email (as a proof).

Usually when I receive a payment, the paypal(automatic email) sends me a confirmed mail but it was sent by the buyer.
also, it says "here's your invoice" instead of "someone(name) sent you $00.00 USD"

The buyer is keep on telling me to read the terms and conditions, which says "we will finalize the transactions within 3 days from today's date"
Should I just wait for the payment to arrive? or did I get scammed?

I have already given him all the information on the gaming account that I sold. 
and if I find out that I got scammed, I am willing to dispute to try to get the money, or just get the account banned anyway..

please can someone confirm this?
I feel like I am worrying too much but I would like to get this checked to prevent further losses in the future.

Thank you and have a nice day!