You do. Plain and simple.
Unless it is agreed on by both parties to the contrary at the outset of a business transaction, South African copyright law is fairly clear in that any person who commissions work that they are paying for, owns the copyright to that work, be it photos, drawings, paintings, music, etc. We have no problem with this and once your photoshoot is paid for those images belong to you.
If there are humans in your photos you assume the responsibility of obtaining releases from them if you intend using the imagery for commercial purposes.