Board Thread:Questions and Answers/@comment-24234144-20130821074045/@comment-8986886-20130821144340

Considering what we know, about how the living standard is highest within Seireitei, and drops continuously as you get farther away from it, the lesser Nobles probably reside in districts 1-10, out of 80 in each cardinal direction. (In districts 50-80, crime is high, and few can afford sandals)

Another reason why they are likely to live near Seireitei, is because that's where the higher ranking Nobles live, and the lesser families often serve the greater Noble Clans.