It doesn't matter how much money you leave in there. Do you have a CC on file or bank account, they might charge it, and even if you don't have paypal might not allow you to do any more business using their platform until all is cleared and you paid if the charge-back goes through in the client's favor.

No, you just shouldn't accept paypal. As k3oni states, it doesn't matter how much money you have in your paypal account. When a chargeback happens paypal will take whatever small amount of money you do have in there, and your account will go negative for the remaining balance... and then the bill collectors start calling.