Kin:
the scams work by paying you more than the asking price, and then asking to refund the overpayment into another account (called shipping account) and if you do that , you never see the difference again.....
also never use Western union for money transfers, once it gone , its gone for good and not traceable and paypal is a similar method to western union that they (the scammer) use.
The only sure way is to get the money FIRST and make sure that you definitely DO have it in your account, or of course cash.
Peter