A millionaire i'm definitely not. However, I think cycling around Africa is probably one of the cheapest trips you could take, with cost of living being as low as it is.
Basically the answer to your question is that I have some savings and i'm saving more this year. I had considered trying to earn money as I go, but I don't think there's that much employment around - especially of the casual type - and I doubt if it would be that well-paying anyway.
The advantage of travelling around wealthier regions: Europe, North America, South-east Asia and Australasia is that you can do the work-travel thing. But I feel the need to travel my own continent first, and anyway as I said, it's cheaper.
Cheers,
Sean