You can't block 0 feedback bidders or buyers.
You can go to your Seller Preferences and Block bidders who do not have an active Paypal account.
- Many newbies don't have Paypal yet. Real newbies have no idea how they will pay.
You can use Fixed Price listing and add Immediate Payment Required.
- The listing stays active until someone pays.
If your newbie pays, ship with Confirmation of Delivery and above all with SIGNATURE CONFIRMATION.
Don't ship except to the Paypal address.
Look up the PP address on Google Maps Street View. Mostly for giggles.