The housing crisis will never end without levying forceful taxes against real estate speculators and investors. A recent report outlines the necessary actions to impose taxes that can actually narrow the wealth gap and alleviate the housing emergency.
Forbid corporate ownership of anything under 4 units/12 bedrooms, and require them own 100% of any contiguous building over 4 units. Added taxes will just be passed on to residents. Corporations are used to aggregate money (both public corps and family/friend groups) and avoid taxes.
Then make a financial law that forbids making property loans with collateral which includes any real property that is not the property being purchased. No condo bros buying units and then re-fi-ing out to buy more.
The issue is owners just fake the documents when your property tax or vacancy tax mail arrives. Friend of mine rents basement suite, landlord has not lived in main house for over two years, it has been empty the entire time. somebody comes every few weeks to collect mail.
Then why not check on it occasionally and put a hefty fine on it when they fake the documents? If you cannot make a new and important law because rich people will try to bypass it than the state is useless.
People forging documents to evade taxes? That's fraud. Put them in jail or if they're a foreign national; take their property until they set foot in the country; then put them in jail.
You'd have to have someone go door-to-door at random intervals for an absolute check, I think, but that isn't a bad thing provided that the people doing it are paid a reasonable wage.
Whistleblower law that lets people who finger this kind of landlord take ownership of the property at a nominal fee for processing the paperwork. Call it $25.
I don't think you have put any thought in to this. How would that solve anything exactly? If you taxed rental income at 110% then nobody would ever be a landlord, and all existing landlords would evict their tenants immediately, leaving millions homeless. Do you just want a system where you can only live in owned properties and renting is forbidden?