In San Francisco city itself, black and poor are highly correlated, for a variety of historical reasons. Most of the long term middle and upper middle class black residents in the Bay Area are in the East Bay. There are fairly concentrated areas of SF which are low income, low development, and primarily black (HP, Bayview) and some areas which became more developed (Fillmore). Mid market and tenderloin have gotten a bit more developed and more diverse (mainly in that poor Arabs and SE Asians moved in 10-15y ago).
Economics and race in SF is really complex.