They often want your email address so that they can send you FAKE paypal emails saying that they have paid and you must send trackable and email them a tracking number before the funds show in your paypal balance = SCAM.
Or they send a fake Paypal email saying you have to send them vouchers or gift tokens to 'expand' or 'verify' your account before you get your funds = SCAM.
Or they send you a fake paypal email saying that they have paid extra but its on hold until you pay the shipping courier out of your own money first = SCAM.
You NEVER see any funds in your paypal balance and never will so be aware.
Advice is voluntary. Kudos / Solution appreciated.