In terms of what to shoot for, a) recurring revenue (BCC didn't have it and _believe me_ did that radically raise the savviness bar required on the customer acquisition front), b) B2B where something is important enough to need but not enough to require a long sales cycle or urgent support if the thing hiccups, c) a well-understood marketing and sales model that you can semi-automate.
The third thing is probably hardest to build, and as your time scale gets longer, it is the most likely part to require your sustained attention to improve. (I have no information how BCC is doing these days but I rather suspect the original organic SEO strategy which served me well for 5+ years will not continue operating unaltered for 20.)
In terms of where these folks hang out: business owners who have priorities in their life other than the business are still business owners. I think the great mistake in the "passive income" community is failure to treat running a business like running a business; it becomes aspirational for lots of folks who have neither the skills nor the inclination to run a business nor, unfortunately, the desire to change either of those two things.
This makes "passive income" spaces into a whirlwind of depression and hucksterism. Meanwhile, if you ask around the table at MicroConf, you'll find some folks who had a really good year and worked really hard for it and you'll find some folks who phoned it in while taking care of parents, getting married, throwing themselves into a home-building project, starting a new business, etc.
MicroConf, BaconBiz, and DCBKK are three conferences which all had folks who were at many points along the spectrum here. All have online ambits to them, too. (I suppose one could run a not-awful conference about software businesses in maintenance mode but if you have one then flying out to a conference would absorb a few weeks of maintenance mode and be probably a lot more boring than going to MicroConf.)