silk-stocking district
A section of a city that is dominated by the upper-class. Even if you had the money, you wouldn't want to live in a silk-stocking district—you'd be totally subject to the whims of your wealthy neighbors.
red-light district
An area in a city containing brothels and other businesses related to activities that are typically illegal elsewhere. If you patronize the red-light district, you're essentially subsidizing the sex trade.