There's also a lot of varieties of digital assets. I am also focusing on increasing passive income even though it comes at a stage when my active income is not certain and shifts from month to month to season...
But I already started learning about and practicing stock photography.(Which, trust me, you have the skills to do, too. I don't know about the time required, though.)
And now also e-books.
Both things are so difficult to start - it's like here on the Steem blockchain - at the beginning you're glad when you make a penny. But it also gains momentum if you keep pushing and becomes better over time.
So not passive ;)
Passive income generally takes a great deal of activity to get the ball rolling on, Steem included. Many people forget the work to get the value to invest, they just see the result of the investment.