Have a look around the Stats SA website, but be selective about how you use the data.
The last time I saw useful demographics in the format that you are asking about was the 2001 census. I don’t think we’ve had a census since. Try Google “South African Demographics”. Pages of mostly useless stuff, but something useful might show up.
It is important to use the statistics of the economically active population. This you can get get in the Census SA 2001 document on the Stats SA website but you will need to make some calculations. I suggest you evaluate the different statistics as per area (municipality, province etc.)