I am in the same boat here. My question is, why do people sell their cameras? Isn't it the same as with some motor dealers where they buy a lemon, patch it up to last just long enough for the 30 days warranty. Or they tell you it belonged to an old Tannie who only drove to church with it. How often do we hear, "this car is giving me so much problems, it is time to sell." Why would someone sell a perfectly working camera?
Is it not the same with the camera guys? Are they not beginning to pick up problems with a camera and then sell it before its starts to give more problems.
Most of us mere or less understands the workings of a car and you can easily pick up something during a test drive, but how do you take a camera for a test drive? How can I trust a camera salesman if he tells me that the camera has only been used indoors taking pictures of Brutus the dog growing up and not during a 'Camel Trophy' expedition.
Camera's dont have small problems that arent undetectable, you will see a problem before you even take an image. Generally people sell to upgrade, therefore they are generally in good working order still. A place like kamarez oftened does a service of the camera making sure it works and works well before putting it on the shelf for sale. They are fantastic.
The best advice I can give is do your research, see what others are using, see what you feel comfortable with and go in more then once and try the camera, go away and consider it, consider which camera speaks to you more and which seems to fit in better with you.
In terms of brand, Canon have the greatest market share in SA but thats not to say they are the best.
Canon and nikon are the bigger names in photography but then there is also sony to consider. Sony are making decent cameras at the moment
Canon and nikon over bundle deals with 2 or more lenses which may be a good kit to go for as you are a beginner before spending money on upgrading your kit. (eg. the Canon 100-400mm L IS USM retails for aboutn 16k, Nikons equivalent retails for around 20k last I looked)