@david3 You haven't been able to find the court case, so you're happy to go along with whatever websites quote whatever other websites that found something that really isn't close to what's happening in the real world now.  Just wait until AI starts manufacturing fake cites when there aren't any real ones.  Anyway, I spent considerable time exploring this rabbit hole when I first tried to track down the sources for those online sources, because I'm more curious than some people who just want a quick and friendly answer.  But it takes me less time now.  The first one that popped up was actually a Social Security ruling on SE tax but it cites this case:

"Thus, the United States Tax Court in Fabian Bobo followed the rule of law laid down by the United States Court of Appeals for the 9th Circuit in Delno in concluding that income from a mobile home park was considered rentals from real estate, unless the services provided for the convenience of the tenants were of such substantial nature that compensation for them could be said to constitute a material part of the payments made by the tenants."

https://www.ssa.gov/OP_Home/rulings/oasi/47/SSR86-12-oasi-47.html#

The case is so old (1978) you can't find it on the Tax Court website, but it's here:

https://casetext.com/case/bobo-v-commr-of-internal-revenue  

And it cites a 1965 Ninth Circuit case, Delno, at

https://casetext.com/case/delno-v-celebrezze 

So if you want to rely on cases decided before the Internet was invented, you won't be the first.  Lots of websites are already doing it.