What do you mean by "own"? Are self-employed people included? What if the business is worth negative money?

If you work and are paid by the hour you're not concerned do not worry

I think it's a bit of a continuum based on the degree to which someone is paid for work they do vs how much they are paid for their position and assets. I think if the business can keep running for a good while without them doing much and they aren't likely to lose their job for it, then they're more of an owner than a worker. I'm sure there are caveats on that.

Literally things like stocks and real estate and cryptocurrency. Imagine Realpage or Bending Spoons.

Then that depends on the corporate structure. If you have personal liability, that means you net worth would be directly impacted and you are personal liable for the business debt. However, if its structured as limited, you could bankrupt the business and the debt of the business get wipe out. In this case, your loss would be limited to the initial investment.

It depends how you separate your personal wealth and the business's

Unsure if you're being deliberately obtuse, but a consultant working for a sole proprietorship is technically making money off a thing they own but they're also still clocking in every day and doing actual work, typically for a third party.

It's a pretty clear separation between those who spend 30+ hrs per week working and those that spend the majority of their waking time "networking" (attending conferences, playing golf, traveling, whatever) with the occasional board meeting or office hours type meeting as the only part of that which looks like a regular job.