as a Seller automatically. You're only charged a fee if you upgrade to the Premium account that can accept credit card payments.

As a Basic account, you can receive payments from other PayPal users whose accounts are backed by a checking account. Basic accounts cannot receive payments from accounts backed by credit cards.

I know, because I once upgraded my account to a premium account to accept a credit card payment. The only problem is PayPal then charges you a transaction fee (percentage) on EVERY transaction - not just on those from credit cards. So all the transactions that used to be free for you are not incurring a fee.

Needless to say, I quickly downgraded my account back to Basic.