First of all, there's no need for a complete expropriation all at once. Having a significant property tax that scales with time would do the trick too. Start wi

First of all, there's no need for a complete expropriation all at once. Having a significant property tax that scales with time would do the trick too. Start with 5%, next year the tax is 10% of its original price, then 15%, etc. After 4 years you lost half of your property, so I'm happy with that, and since it's all about percentage like other taxes you should be happy too. And then, all this argument is basically a straw man, because there no need for the state to guess anything or to set threshold, at all: all you need to do is mandate people to declare their primary residence, and in fact it is the case in many fiscal system already! If it is your primary residence, then fine, you can leave it empty for as long you want, as long as you are not lying on the fact that this is in fact your primary residence (and if you're lying, then the state must gather the evidence and win against you in court, which is what the rule of law is). Tada! Imaginary problems solved.