Hi,
That's what Vikas had said.
You can only buy options with the balance you have.
But if you want to short any options, you should have the balance equal to the margin of the future(stock or index).
For.e.g if the margin of the nifty future is 35000 and you want to short CE of value, Rs. 100 one lot, then the total cost of the option is Rs.5000 only, but the margin equal to 35000 is blocked during the trade.
Rajiv