The bubble pops when property is not as safe/lucrative of an investment as other instruments, and the foreign investors sell up. House prices go down, but no one can move because their mortgages are underwater (proceeds from selling the house don't match the outstanding debt). Developers stop building because no one will buy the new-builds at a price which will leave them with a profit. The situation is as before the bubble pops, but now everyone is poorer since their (inflated) home equity has vanished.

Usually this happens when interest rates go up, because then it's better to keep your wealth in a more liquid investment like cash. Mortgage payments go up as well, turning the (imaginary) loss of equity into concrete loss of income.

The bubble pops once the big development firms start going under. At some point, the highly leveraged property developers will stop being able to clear out the apartment blocks they're putting up presuming $1m+ sale prices. They're the ones who pop the bubble, since a few bankruptcies are very likely to cascade into panic selling.

They go under when buyers stop showing up. It's the buyers. Think: where does their money come from? (from buyers)

Lots of countries don't allow foreigners do buy property in this way to prevent exactly this sort of Bubble.

What might be happening (I think, seen no evidence yet) is that asset managers in banking have moved "safe" money from treasury debt to real estate, because return from treasury debt has moved to close to 0 since 2008. The result is billions of dollars have moved into real estate across the world, fueling what seems to be an increasingly global real estate crisis.

It is a bubble as it only continues for as long as the government allows - eventually the house owning majority will die, the next generation will be jaded and demand stricter controls. I guess that's what the locals have over the rich internationals, a vote.

International gentrification?