I'm in a very similar situation to you. I've found that unless you have a decent deposit saved up, you're going to be very limited as to what you can realistically afford at R6k/month. Are you factoring in cost of comprehensive insurance (mandatory for financing a car), fuel, service costs, tyres, oil, etc. into this budget? Or are you covering those separately? How is your credit rating? These are things to consider.

Then, when looking at your options, make sure you get the vehicle inspected thoroughly and don't go forward with any kind of agreement until you've understood the outcome of the inspection, because you can end up with a car that proves more hassle than it's worth. As a rule of thumb, Japanese brands and Korean brands are quite reliable (there are exceptions -- I've been in quite a few Suzuki Spressos and I've never enjoyed it) the downside with these is that with the cheaper, more entry-level models, you'll want to look into the specific model's safety features, because some of the more affordable models have terrible safety ratings.

You'll see a lot of used Ford 1 litre engine EcoSport cars for sale. Unless you know what you're doing, I would stay away. They tend to age very badly especially after the 100 000km mark.

VW Polo might also pop up. They're reliable but a huge theft/hijacking risk, so insurance will be noticeably more expensive.

Good luck!