PayPal is transaction processing service that allows you to accept credit cards payments, thus there are fees regardless if you are a non-profit or not. The advantage is your donors do not have to have a PayPal Account to make a donation, they can simply use the guest feature with a credit card. You did the proper action to setup a Business Account for your charity as there are certain requirements should you choose to use a Personal Account instead (but, there still would be fees, fundraisers that are not verified nonprofits will be asked to demonstrate how their donations will be used, once they raise more than $10,000). If your group or organization is a registered non-profit or 501(c)(3), you can qualify for a discounted rate.
In theory, it's possible you could collect donations for "free" however, all of your donors would be "required" to have a PayPal Account and all of your donors would have to use the Send Money feature and choose the "Friends and Family" option and they could only use funds from either their bank account or their PayPal Account balance. As an option such as this would not really be practical and there's a chance that activity such as this could possibly be flagged as suspicious, I don't think it would be worth the risk.
