Wow I just looked up Sunset Valley, population 700 and a median household income almost double that of Austin. They get fire, EMT and education services from the larger Austin area, but provide their own municipal police. Obviously all this requires a mayor and 5 city council members to manage.

There is even an enclave within the enclave that carves out a single medium density housing complex. Can't have the unwashed masses using any of THEIR community resources.