You ask, really, is this possible? The South African government is considering it to appease rhino farmers. Rhinos do not have to be killed to harvest their horns which actually grow back if cut. As a consequence South African rhino farmers think if they raise rhinos for their horns, they can get a big pay off from the constantly increasing demand for rhino horn.
Rhino horn trade remains illegal and rhino horn demand continually increases. In Asia the Chinese use it in medicine, mix the powdered form into mixed drinks, and give it as luxury gifts. Of course, there is no proof it works for anything. That seems not to matter. Currently, although it varies from time to time, powdered rhino horn brings about 60,000 dollars per gram, more than cocaine, gold, and heroin combined.
The logic behind farming rhinos is that farmed rhinos, usually white rhinos, will provide enough for the demand and save wild rhinos, especially black rhinos which in some areas are already extinct. Research indicates otherwise: that once rhino horn is legalized, the demand will increase far beyond what rhino farmers can supply. A study by Duke University indicates that many, who do not currently buy rhino horn because it is illegal, would buy if legalized. Once the demand is greater than farmers can supply, poachers will kill whatever is needed to fill the demand.
If you want to research this and discourage the South African government from legalizing rhino horn trade, go to this website: nrdc.org/rhinos.