Money 1.5 crores as deposit to NSE. Another Rs 30 to 40 lks as upfront tech costs if you use a vendor. Office/people cost extra.
Time: 1 year getting NSE/SEBI etc
Experience: Exchanges ask for minimum 3 years experience, but I guess if you are convincing enough, they’d consider.
The above is for NSE only, if you want to be broker on other exchanges you have to add more.