In anthropological perspectives, I am particularly interested in marginality in the urban settings in Africa. I have already done on it from the historical perspectives, on sanitation and public health in colonial Africa.
It sounds like you'll also need to look at the political and social restrictions of that society to help you determine what options such marginalised individuals had economically? Did they have access to education, healthcare? What resources could they access and afford to access? If this is colonial Africa there should be a lot of biographical data?
Attempt to open the complex social structure (incorporating the marginalised urban) and place it in the dynamical space of the country, tracing back to independence. Enjoy the challenge.