"All of this is true, it is unethical and illegal. But it is also true, that in cities like San Francisco and NYC (especially SF-Co) rents are absurdly high, and landlords care nothing other than making the most of it. My previous two landlords forced me to pay only cash for rent, and I know many other landlords do the same, and cheat on taxes."

Way to go on painting every single landlord as greedy bastards who care about nothing other than squeezing every single penny out of the tenant based on your own personal limited experience. Don't be so quick to generalize that all landlords are slumlords. For every story of landlord abuse, there is one for tenants who take advantage of the system as well.