Paypal has an affiliate program but it can be tricky to figure out
how to sign-up for it.

Here's how:

It's hard to believe everybody doesn't have a PayPal account, but some
people don't, and many with good reasons. Many people starting online
businesses may have been buying stuff for years online without having a
PayPal account. Since PayPal allows purchasing through it with a credit
card but without an account login, many people will...