Second house/vacation house (not rented): Multiply property tax by 10.
Rentals (including airbnb): If mortgaged: Max the rental (monthly and daily) to 1.1x Mortgage amount + yearly property tax amount / 12. Unmortgaged: Property tax amount * 2 max per monthly income.
Change the maximum amount you can sell a house to be equal to cost of materials plus 30 days of labor for 5 people.
Owner builder homes can get a 60K automatic grant - everything must be verified - and limit land HOA rules that specify a minimum sized house.
Make "Limited Density Owner-Built Rural Dwellings" possible in areas that are not affected by fire.
Finally to make all this feasible - make junk properties illegal (noise limits + junkyard style land usage)
It would solve a lot of NIMBY issues and please the YIMBYs. I have a billion other crazy ideas like this.