Yes, you need a visa and apply for it before leaving. THe same if your friends go to Your country. THsy should have visa too. It need to fly 14-15 hours from South Africa to China. From Cape Town, you can fly to Xiamen of Fujian via Hong Kong and Singaport. There is not direct flights, I am afraid. Sorry, I have no idea about the price, you can make a inquiry by calling. :-)