It sure is possible anywhere around africa you can backpack.
The locals would be more than happy to help you out as well. A bit of excitment for them helping someone find a car to buy (keep in mind they may ask for money for helping you!!) about 10 years ago
Just a note if you are looking at buying/selling a car in Kenya there has been a question about this already and someone answered via twitter which I posted up.
http://travellr.com/questions/kenya/387/were-looking-to-buy-a-second-hand-4wd-from-kenya-in-june-2009-has-anyone-any-contacts-or-ideas about 10 years ago
Yes! Depending on how long you have. To get around South Africa go to http://www.coastingafrica.com/ Start there then as you meet people you can probably share a ride with some to get yourself around. There are some links in there about buying a car then they buy it back from you www.driveafrica.co.za
good backpackers in Cape Town is Ashante
You need a solid 4wd for driving in Namibia. Roads are dusty and some are full of stones. Spare tyres a must.
Botswana is a bit more difficult to backpack through. You'd be best to do a camping safari. jenman safaris in cape town are brilliant.
Start in Cape Town as you'll find there are a lot of like-minded travellers. Enjoy! Travel Safely. almost 10 years ago