yuppie slum
n. An upscale neighborhood populated mostly with young professionals and managers; a neighborhood with older and slightly run-down houses that young professionals purchase and renovate.
Examples
1999
The 20th annual Los Altos Arts & Wine Festival will bring a throng of Abercrombie & Fitch-clad visitors today and tomorrow to the quaint downtown. Rolling into this upscale lion's den, minus the Clydesdales, is Budweiser's Mobile Beer School, in a bold attempt to lure members of the microbrew-and-wine set off of their high horses. … But Sam Bradley, who pours drinks at the Los Altos Bar and Grill, said the town's reputation as a yuppie slum is undeserved.
—Marshall Wilson, “School That's Good for What Ales You,” The San Francisco Chronicle, July 10, 1999
1993 (earliest)
Victorian "bay and gable" houses populate Cabbagetown, sometimes described as the world's biggest Yuppie slum because in recent years it has been discovered by young couples attracted by low rents and the challenge of restoration.
—Jay Clarke, “Toronto at 200: Ethnic enclaves spice North America's greatest melting pot,” The Miami Herald, July 25, 1993
Notes
It seems like the word yuppie (derived from the acronym of the phrase "young urban professional") has been with us forever, but it only entered the lexicon around 1982. It fought a pitched battle with the rival terms yumpie (based on "young upwardly mobile professional") and yap (based on "young aspiring professional") but yuppie proved to be too strong.

It was only a couple of years after yuppie first appeared that a new verb was coined: yuppify. In terms of this phrase (which was spied by subscriber Alice Reich, by the by), it means to create a yuppie slum like the one described in the second half of the definition.
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