What is actually a minimum initial investment amount in a mutual fund SIP? Do I need to have that amount in my bank account ready for transaction?

The minimum investment amount for SIP is different for various funds. Once, you have clicked on the SIP option of the particular fund on the MF platform then it will display the minimum investment amount for the first order and then the minimum amount for subsequent installments.

As you are required to have a zerodha demat account for purchasing the fund from the Zerodha MF platform thus the amount will be deducted from the trading account. So, the inconvenience caused with respect to going to the bank and activating ECS and other issues are avoided.