There is no age limit for trading or investing. Once you feel you have become independent, have acquired enough knowledge, have sufficient capital and experience you are in the game!!!
there is no valid age but you should be mature enough and should have adequate funds to invest and should have a valid PAN CARD
Introduction to stock markets at your early age is good as the mind is more flexible and eager to learn at that point of time. But, at the same time can you handle the loss and pressure that comes with it.
Learn technical analysis.
Start with virtual account. You can use nse pathshala.
Read my jouney into markets http://bleedingmarkets.blogspot.ie/2016/05/my-journey-into-markets.html
The early the better…just think If you lose money at the age 20, you get ample time and opportunities in life to recover you losses…but if you lose at the age 60 then how much time you have to recover…??
For me starting at an early stage along with studies is beneficial because winning in stock market needs experience and if you are not successful in it you can pursue another career and have ample amount of time to recoup your losses. I personally started when I was 19 and now I have 1 and a half year of experience and 2 lac of losses to recover.
thats what I mean…!!