you can't both expect profit and good maintenance. pick one, or the other. in all things. that's why roads aren't privatized. or the fire brigade. etc.
I care less about the number of units the landord has(within reason) than where they live. If a guy wants to rent a dozen units a few blocks from his own house, fine. But some asshole 5 states away renting a house he's never going to lay eyes on? Fuck off.
Housing needs to be about housing, healthcare needs to focus on healthcare.
That's why I think profit needs to be eliminated from the equation. With it, the priority will always be maximizing profit, with providing a quality product or service being secondary, or even incidental.
Not just withholding rent, punitive judgements on anything less than best effort on dealing with it as soon as it's known and inspection schedules that keep the longest duration it can be unknown for short enough to avoid most health issues.