Thanks for the great question.
~ Very sorry for the delayed response on my part.
This plugin works in conjunction with PayPal®
Website Payments Standard, for businesses. You do NOT need a PayPal® Pro account. You just need to upgrade your Personal PayPal® account to a Business status, which is free. A PayPal® account can be upgraded from a Personal account to a Business account, simply by going to the `Profile` button under the `My Account` tab, selecting the `Personal Business Information` button, and then clicking the `Upgrade Your Account` button.
Now, if you purchase the s2Member Pro ( add-on )
*PayPal® Pro Integration* You will need a PayPal® Business Account, w/Pro Service. PayPal® Pro accounts require a formal application, along with a small monthly fee. Once you have a PayPal® Pro account, you'll need access to your PayPal® Pro API Credentials. Log into your PayPal® Pro account, and navigate to Profile -> Request API Credentials. You'll choose ( PayPal® API ), and then choose ( Create Your Own ).