I don't think my heart is in the business of things. I look at people like Linus Torvalds or Larry Wall and see guys who developed their own projects and somehow made a living doing so. What is that "somehow"?
2. Work hard on the project for a continuous period of time.
3. Be fortunate enough to have picked something that the rest of the world wants.
And then your chances are still a "maybe". So you can't necessarily plan for it.
Think about what that would take nowadays. Create the next iteration of Git or Linux, something that replaces either of those?
It's a high bar to clear. Not saying it's impossible, or that you have to clear it in order to be successful as a solo developer, but when you're invoking names like Linus and Larry, you should know what kind of mountaintop you're looking at.
You can't plan for superstardom. Unless youre selected and made one which doesnt really happen in software.