Most members of the black middle class that developed in the South in the late 1800s worked as what?

In general, the black middle class that arose in the South
after Reconstruction came from a small class of entrepreneurs who provided services (and
some goods) to fellow African Americans.  African American businesses were not going to
be able to attract white patrons and so black businessmen had to cater to other
blacks.

Much of the middle class worked as
semi-professionals.  There were ministers of black churches and there were black
undertakers.  There were also operators of small grocery stores, barber shops,
etc.

In other words, the black middle class did not spring
up by working as management or white-collar types in big businesses.  Instead, they
tended to be small entrepreneurs catering to an African American
clientele.