Do I have to link my card to PayPal?

Paypal limits accounts that are not verified with either a bank account or card or file. The limit is around $500(money that is received or sent as in a payment) and after that any funds in your account will be locked. If you are receiving money how will you get the funds out of your paypal account? By linking a card you can transfer your paypal balance to it. Sorry I do not know anything about Adsense...