If you want to become a member on all the exchanges, deposits of 1.5 cr for NSE, around 30 lks for Bse and 30 for Mcx-sx. For Mcx another 15 lks. Membership fees of around 20 lks for all exchanges combined. If you want to offer equity and commodity trading, you need to have your own platform, around 50lks more for that to begin with along with the back office. So around 2.4 Crores in refundable deposits and cost of around 60 to 70 lks.
But yeah what can really add up to a lot are the continous compliance and technology costs. The brokerage business in India probably has the highest number of regulators.
Documents required are available on NSE site in the new membership section, and they also ask for some relevant experience from people starting the business.