Then they should lease it meanwhile or pay the tax, it's rare for people to buy houses fully finished, say, a year in advance.
>- Maybe they haven't found a suitable tenant yet.
They can lower the price to find a suitable tenant faster.
>- Maybe they are holding it open for a friend or family member.
Then that friend or family can move there officially while still occupying their current dwelling until the grace period expires again.
>- Maybe they want to do some renovations before renting it out.
These laws in practice have an exemption for rénovations.
>- Maybe they want to sell the property and it's easier to sell without an existing tenant.
Then they should price it as to sell within the grace period, or pay the tax.