To be completely honest, I don't see any passive income that isn't a scam. HYIP sites are "passive" income because you just send you money and then the website will make money for you. That's what HYIP sites say, that's what they promise. But, they are all just a scam. It's too good to be true, I won't even go near somewhere HYIP sites.

I think the only way that you'll earn some passive income is when you have your own company. It would take a lot of hard work, and you would have to hire a lot of people. A lot of money will be involved. When the company goes booming, you'll earn money as if it's a passive income because you don't have to work at all anymore. The people that you hired will be the ones doing the hard work and you're just there resting, watching your bank account's balance go up.