And your work per month could be contracted out, so you don't actually need to do any more effort than meeting with your account periodically to make sure you're making money.
He probably turns over something like $20M, and can use the portfolio to write off profits from other businesses.
Someone who bought their home before a price boom can often turn a profit because the rents follow the price to purchase (roughly speaking).
So if you acquired a bunch of properties in 2008 after there was a crisis, its likely that they're very profitable (month to month) now