An rv storage lot has got be one of the easiest incomes.. and great margins too.
Man where I park mine, it's a big slice of unincorporated land within the town limits. 20 acres, there are ~600 slots there, at about $130/mo average.
It's a crushed asphalt lot, a fence perimeter, an automatic gate with keypads, and that's about it. There is a sign on the gate with a phone number and website for any potential new renters or current ones with issues I suppose.
$80k a month, and this guy has ZERO employees, very little operating costs, doesn't have to show up (there isn't even an office), and he bought the land 25ish years ago, so surely it's paid off. Most of the growth of this town is newer than that, so he probably paid a few grand an acre.. now worth more like $100k/ac if not more.. but who in their right mind would sell land for just a few million that's making $1mm a year?
You go to website at any given time, and there are maybe a dozen available slots.. this thing is perpetually full.
Guy hit the jackpot when he bought that land. I met him just one time, a dude in a land rover checking out the construction on the road at his entrance, so I figured it was him and said hi. He was about late 50s, maybe early 60s.. so I'm betting he hasn't worked a day since his 30s.