It depends how smart the person is !! Some of the excellent traders started as teenagers under the 20, others have been trading for ages and all what they do is write books , give an advice and or about what the market, but they can't make money from trading. With time comes experience but not all experienced traders are successful. I think 2-3 years should be enough experience in trading, as by two years you should be able to read the chart and know where to play.