> owning real estate that someone else manages or really owning any business that someone else fully manages for you

If you've ever owned real estate or a business you'd know it can't be 100% passive. Even with a property manager, there are always things to fix, change, or update, and the associated decisions to make about it. One bad tenant or a property manager with bad judgement, and you're 100% back in full-time landlord mode to clean up the mess (literally or figuratively).