Honestly I recently looked at getting something to go to the shops with, dump gardening supplies and plants into and possibly use in bad weather (M5 is interesting in wet weather)
Under R50K I found mostly scams and garbage. Old cars and bakkies needing WAY too much overdue maintenance or repairs to be viable vs. buying something newer at R75 or R100K. Very high mileage, very poor paint and interiors (even beyond what you would expect when paying between R40 and 50K). Be VERY careful at this price point IMHO, unless it is something special where spending some cash off the bat can be justified.
Please also check the fine print of some of these 'dealers'. Many show a price that is on the high side for a good example, yet they are in average or below average shape (my opinion). They say it is a wholesale price as is, usually not negotiable and then tack another 10-15K on in warranties, admin etc. if you want to finance (on more expensive, newer cars) or want any kind of recourse from a CPA perspective.
I've owned a very high mileage E36 before. If I could find a good one in the right spec and price I'd buy one. However I can also do work myself and can pay to have work done that I can't do myself. That has to be factored in if the ENTIRE budget is R40K. There was one that was being invoiced as I arrived at the dealership a week ago... such is the nature of looking for these kinds of cars. I wouldn't mind a Honda Ballade or Civic at that sort of price point from a reliability perspective but good examples of all brands are sold QUICKLY (few days) at that price point. Check out the forums and groups as well, not just gum and OLX
Heading to auction tomorrow to see if I can find anything. However a lot of cars go for close to what you would pay at a dealer anyway.