The solution to buy-to-leave is surely extremely high taxation on properties left empty (and I'm talking "10% of market value" levels of taxation, enough to obliterate any possible returns on investment).
That would be either unreasonably punitive or easy to avoid. Properties needing renovation or structural work can't reasonably be penalised for not being occupied, so owners would simply arrange for unoccupied buildings to be permanently having work done on them. I'm sure there are plenty of builders that would help them out for moderate fees. I'm sure there are other ways round something like this too.
Or you can just keep the taxes on unoccupied properties and people will make sure they get fixed up quickly. You'd be surprised how quickly and efficiently work gets done when penalties for lateness are high enough.
> That would be either unreasonably punitive [...]
If it was levied on the value of the land alone, there's no such thing as unreasonably punitive: land values would just drop until the tax is priced in.
If you look purely at economic efficiency, and leave out any morals about _who_ should be taxed, the only thing keeping taxes from going up all the way to taking everything is economic inefficiency. Ie if you heavily tax a particular widget, people will produce fewer widgets.
Land is fixed. You can't produce it, thus no tax can interfere with its supply. (Unless it's a tax system that incentives you to keep your land off the market, like negative gearing in Australia (https://en.wikipedia.org/wiki/Negative_gearing).)
However, if the tax was levied on the value of land plus building on it, a high tax would discourage building houses---whose supply is emphatically not fixed.
That's fairly easily dealt with. Require it be occupied for more than 6 months of the year, otherwise 1% (or 0.5%, whatever) of market value per month unoccupied. 80% of construction costs can be subtracted from any unoccupied housing fees applied. Any fudging on the construction fees paid/received is tax fraud on one or both parties.
I really like this idea, except that "market value" is vague, and would require a bit of work to determine accurately. Maybe the best you could do would be to have a by-block square footage to value chart to be used for these purposes (and you would want a definitive source anyways, to prevent gaming the market value side).
This could also help quite a bit with the property owned in New York as a way to launder money[1].
It seems like a cute solution. But it's a bit unnecessary, and complicated.
Ie you probably would want to tax under-occupation as well. (Otherwise you just declare a bunch of apartments as a single unit, and have a single dude check in every once in awhile. They did that in Britain, because of different legal treatment of trespassing between empty and `occupied' buildings.) But how do you define under-occupation? Where do you draw the line?
Just use a land tax. It's simpler and harder to evade.
