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There's no way to buddy anything but credits on here. I think money can only be transferred into your account by you while you are logged in so they'd have to give you their Paypal info for you to take their money or you'd have to give them your login to allow them to long into your account and add the money. Neither of which is something either should be willing to do.
The closest you'd be able to do it is to have them PayPal you the funds and then you transfer it into your PBs cash.