Can confirm, I work for a company that helps landlords finance the purchase and repair of rental properties.
In certain very LCOL urban areas around NYC and Philadelphia, we have individuals with tens of millions of dollars of property spread out among ~$150k buildings.
They inspect their portfolio with armed bodyguards, and they very often own other businesses in the same neighborhoods that throw off money in small but regular amounts: laundromats, bars, clubs.
An an interesting aside, these individuals are almost all involved with close-knit religious groups to which they contribute great deals of capital.