When buying a chameleon check out the animal and the source carefully. Is the animal in good condition? Does the supplier know what they are talking about? There are some excellent pet shops who will give superb advice... and there are some that are not. Don't buy just because its cheap; the costs come later!
Read everything you can before you buy. QtCreaCha is quite correct about her advice that the cost of the animal is only a part - a small part - of the expense. If you scrimp on any of the things she's mentioned you will end up at the vet with a sick animal. Supplements and UV cannot be avoided; cages should allow good ventilation. If you do decide to use a waterfall (not my choice) then it must be scrupulously cleaned, almost daily to avoid bacterial issues. Think about the food you will offer; can you get it? Do you want to? It will need to be balanced and gut loaded crickets are the simplest.
When the weather is right we keep Veiled in an aviary and they thrive. With the natural sunlight there is probably no need for a basking light with the risks of outside electricity. Watch the night temperatures. Don't let it stay outside if it is below 10c. At the moment it is too cold for keeping any species outdoors (you said you lived in Joburg). If you are bringing it inside you must be prepared, with all the right equipment, which may not tie in with what you were saying about the Flap neck.
As QtCreaCha said, if you can do it properly, then go for it! Awesome animals.
There is a care sheet on our web site and you are welcome to email for advice or comments.
David
http://www.sa-chameleons.com