Do you have a link where we can learn more about these opportunities?
The big ones are flippa.com and https://empireflippers.com/ , but the deals there aren't good. But you can learn a bit about affiliate marketing just browsing the projects.
I understand why some others have said those returns sound unbelievable. It's because they aren't completely passive. It requires absolutely zero skill/effort to put money in the stock market, mutual funds, etc. It requires skill and effort to put it into an online business and maintain or grow that business. Most people can't (or won't) do it.