"passive income" means regular income that does not require your activity. Common examples are bank interest, stock dividends, real estate rent, copyright or pa

"passive income" means regular income that does not require your activity. Common examples are bank interest, stock dividends, real estate rent, copyright or patent royalities. In the big picture, some activity is eventually required, it's just a matter of time - books fall from favour, patents are superceded, even banks can go, well, bankrupt. So it's a question of degree, and of how much return. Of your suggestions, SaaS requires a lot of ongoing work. Most books and games have hit or fad-like popularity - so a low chance of on-going income after you are done. Your "niche" idea is the best of the three - but it's completely dependent on finding a niche that is under-served, and will continue to be under-serves. That way, the income can continue for as long as the technical niche exists (it eventually will be superceded, and perhaps the surrounding ecosystem also swept away). The downside is you generally can't make much money this way - but you didn't ask for that, so it's fine. Remember the saying "you won't get rich writing books". So the tricky bit is choosing the niche with these market characteristics AND that is personally easy/interesting/attractive to you and not to others. BTW: I wrote a couple of chapters for a book, got a decent advance on royalties, and IIRC about $4 royalities after that (most books don't "eat out their advance"). This was on a technical topic, but not really niche. A word on passive income: I succeeded in this with a software product... but discovered that my life became about invoices, negotiating license terms and international taxation law. I was so much happier actively developing! Since you'll end up doing something, I now think active income has a lot going for it! [Of course, you're only requesting some passive income, so this may not occur.]