Regarding the infrastructure you need to calculate per seat/system.
usually it should be cheap in chennai compared to bangalore.
To start with you can have 25 agents for some outbound campaigns.Because inbound might be difficlut to handle compared to outbound as you need some type of experience to handle inbound.
You need to have a good location with basic amenities like transportation and telephone exchange and you need to have a IPLC line which should be approved from DOT and licence to start a call center plus systems/head sets/furniture etc.
If you want to a turnkey project we will be able to help you(Along with the campaigns).
please let know your contact details. I will send you the entire revenue model.