When I lived in Chicago, I had a buddy, earned a decent amount but not like an insane amount, bought and rented out a place .. and then another ..and then had four. One of the places started off as an AirBNB, then the woman wanted to rent it out, then she stopped paying rent after the first month, and it took 5 months to finally evict her. You go through the process, then you gotta wait for the sheriff to be available, and they call you and you have to go evict them right then. The bitch even showed up as they were dumping her shit to the curb. They had to use gloves as there were needles .. and probably meth ..everywhere.

Even place I've rented that was owned by a person (even real estate people) had a for sale sign in front of it in a year or two. I was even offered two of them at a discount.

If you can get some really good tenants, and you can pay each mortgage and save enough to self-insure against bad tenants ... and you can deal with all of the terrible bullshit that go into property management ... yes you can have 10 hours by 30 and it be good. But it just rarely ever works out that way; unless you a super asshole or really good at being a slumlord.

TL;DR yea I agree that's dumb advice.