How to pick a side project strategically

If your project can't attract any users, then it's obviously not going to generate any meaningful revenue, let alone allow you to eventually build a business around it.

Too much monetization potential, on the other hand, can attract regular businesses, or venture-backed businesses. So ideally, we'd be somewhere in between.

You can't undertake a massive project on the side, so the scope needs to be minimal. Once an initial version is live, it should be extensible incrementally. Adding many small features that add up to a great product. Since side projects are primarily done in the evenings and weekends, the available time is usually chunked into sessions of a couple of hours.

That's another reason to find something that can be built iteratively. Try to ship something every other session.