Legal issues
If you are going to employ staff then you must register them with UIF and SARS. You should also notify your local council that you are running a small business from home as there maybe zoning regulations that you would have to take care of.
If you plan on running a home-based business that will have no employees and no walk-in trade, the zoning question may never arise. If employees or customers are coming and going, making noise, or taking up parking spaces that would normally be used by residents, you can expect neighbours to complain and report you to the municipality.