I have been doing some research regarding becoming a payment processing agent. Essentially you sell credit card processing machines to businesses and make a commission on EACH transaction.
Although the percentage is small (%0.5 + $0.50) per transaction, it adds up if you have multiple clients. Going back on the idea of getting people to pay you, rather than earned income. Below is a link to some good reading material. If anyone has tried this please post below. I know this isn't technically "passive" because you're going to do work maintaining the hardware, but it is still interesting. So let's talk about this! Thanks!