If you own a rental in San Francisco, you have an effectively zero-risk investment.

Is it a zero-labor investment? Fuck no. But, due to the city's completely batshit insane zoning laws and the militant NIMBY contingent you (as a landlord) are guaranteed an income that increases far more quickly than the cost of maintaining it.

It is for this reason that most landlords in absurdly high-demand areas get no love or sympathy whatsoever.