I have a passive income farm of android & windows vm's running a few apps that people recommend at https://www.reddit.com/r/passive_income/ and other subreddits. I'm being intentionally vague about the specifics because demand is far less than supply.
I liked the idea of investing in hardware to earn money without actually doing any physical work. I started with mining about eight years ago, but electricity costs take away a significant portion of your earnings and add an incredible amount of heat and noise. My first mining rig was 4x 6950's with a Sempron 145 in 2012. I made enough when bitcoin hit $1000 but since then I've grown averse to the entire concept of mining with computer hardware.
But I still wanted to pursue the idea of passive income so I looked up what people were doing with phone farms, and stepped into virtual machines not long ago. A 3rd/4th gen quad core system paired with 32gb of ram can host 20 vm's, each of which can potentially earn Rs 100-150 per month these days.