I'm not too sure if this is a well known method or not. But it's been working nicely for me. This may not work in the US due to gambling laws... but I'm sure you can find your own spin on this.
Ok so I signed up as an affiliate for two online bingo sites. I went for the revshare option. If you look around you can find 35-40% revshare easy.
I then created two domains and set up a redirect on each of the bingo sites through my affiliate link.
I then got some double sided flyers printed. On each side was one of my domains along with information about an attention grabbing offer from each site (like free £10 no deposit play for example). Make sure the flyers are very cheap to keep your margin, low quality paper and black and white ink will do.
I then started delivering them to low income housing (more likely gamblers!)
You do have to deliver a lot as conversion ratios aren't great. So you will have to get thousands of flyers and this means paying some kids to help deliver them.
But because you are getting revshare on total liftetime earnings from any hits you get, just a few weeks work delivering some flyers can result in continuous passive income for years! Especially if you hit some gambling addicts.