I have been facinated by this for a long time and must conclude, there's not really something like passive income. If you think about it for a moment, all the blogs about passive income, they spent huge amount of time bragging how little they do, because what they do is to sell you a dream about a easy life.
But there's something you can call independent income, which allows you to move freely, work when you want and scale as you like or need to. It will still require a lot of work, nothing comes for free (almost). You would have to do things like accounting too and there's a greater risk than a regular job.
If you can manage it, I can say honestly it's a great way of living.