The Slave Narratives, compiled by workers from the Federal Writers' Project from ex-slaves and their families in the 1930s will give you loads of information. Most interviewees give their occupation or means of support somewhere in their interview. Jobs ranged from field work, laundry work, cooking (either in people's houses or in restaurants), teaching, day laboring, etc. It was really a mixed bag; there are literally thousands of interviews, in something like 33 separate volumes.

Edit: Also, many of the interviewees received "old age pensions" (Social Security) and "commodities" or other government assistance, or pensions from their retirement. A fair number owned their own homes, or owned land, sometimes even farmland or rental properties.