There are also proxy holding for people laundering money from businesses like Drugs et al, which as you have come to see, are "illegal" . Indian magnates have also been investing in real estate in the country.
However, most of the money has been the $ 1 billion that the Treasury can't account for.
An IBM executive , South African native once said, "Its crazy to pay rent of Kshs. 130 ,0000 a month for a fully furnished 1 bedroom in Westlands. There must be some unexplained money coming form somewhere for people to be ready to pay such rents. "
South Africa has a stringent cash flow policy, and a sudden influx of cash in your bank account will lead to it been frozen, till you can explain how.