After 25 years spent selling premium real estate, de Keyzer has become increasingly attuned to the idiosyncrasies of the global wealthy. Middle Eastern buyers won't consider houses without elevators. Singaporeans require lots of staff accommodations. Russians, on the other hand, have few servants and consider privacy and security paramount. Indians like his-and-her walk-in closets. Americans tend to window-shop, preferring to rent for tax purposes.