I have four rentals. Each cash flows about net $300-500/mo or <$22k/yr. ($750k value w approx $280k in equity.) In hindsight, I would have preferred to VTSAX and chill. I hire a property manager so I am not very hands on, but if/when something does happen, it wipes out entire year earnings. Ex: replacing windows…easily $4k. Turnovers and needing to renovate the place after 7 years… $15k.
I have a buddy who cashed out his retirement savings, rushed into 3 properties that are pretty run down, and now stresses about repairs because he doesn't have the cash on hand.
He wanted to be a slumlord because he didn't want to work a job, over-leveraged himself, and is now stressed all the time.