At least 1000 immigrant millionaires have spent the million buying a house in Auckland over the past few years. These are houses that would have sold for only, say, 950,000 if those immigrant millionaires hadn't been in the buyers market, so I guess that's created an extra office job or two at the local banks and real estate offices.

An immigrant billionaire might buy a mansion with airfield attached for his armageddon hideout. Or he might grow a business employing immigrant workers on work visas. Some citizens might get jobs in the service sector servicing them.