I know of one school at Wonderboom in Pretoria who do that kind of thing but they require that you do your whole PPL/CPL/MEIF/Instructor course with them. No harm in giving it a try of course. You can contact Udo on +27-12-543-3050 for details as he runs the school but it may be a problem that you trained elsewhere.
Your main problem may be work permits due to the number of locals who are also doing that kind of thing. If you can offer something like instructing in a foreign language (Strine and Kiwi don't count) you should be OK.
Good Luck......