guys also i got one tip.
yes yes im new here but still a tip is a tip

well this one cost you a bit money.

when you feel suspicious on him,ask him/she to give he/she's address and said to the seller that your goin to send a letter to the seller and ask the seller what is written in the letter.

Questions:
why should i ask the seller's address?

The point you ask for his address is so if he scam you,you can report the address to the police