...the biggest reason middle-class rentals are disappearing is because there's no money in it. At best, you might cover your costs, but more likely costs will exceed income, by as much as 50%. Who in their right mind would own middle-class rentals when they're so likely to be a financial loss??
It is far, far cheaper to rent. Yeah, you don't build equity, but you also just pay rent. You don't pay tax, insurance, and maintenance that exceeds the value of a middle-class home, and which can bring your total outlay to half again more than the mortgage payment.
Home buying benefits realtors and mortgage lenders a whole lot more than it does home buyers.