You dont have to put money INTO a PP account. You just link it to a checking account or credit card in order to buy things. When you do the funds just pass thru PP from the checking or credit card. When you receive money is does stay there (and earns a little interest) unless and until you withdraw it to the linked account.

They dont like you to just have a credit card attached, I think because it gives you a way to win disputes without them. Without a checking linked, you can do something like $2000 (maybe less now, maybe a fixed number of transactions) before you have to link a checking account to do more transactions.

They also support eChecks, but I have never used it.