Hello Sumit,
NASSCOM-McKinsey Report 2002 estimates IT Enabled Services (ITES) market which includes activities like Call centers & back-office processing operations in India to be a US $18 Billion industry by 2008. This is in upward revision to the earlier NASSCOM report report on this sector couple of years back.
The sector has seen amazing growth and proliferation in number of call center facilities set-up over last 2 years.
Most important factor responsible for succes of such an operation and specially a telemarketing center is people. Since most telemarketing contracts are success based payouts, you need people who can convince & close a sale over phone. This is a volumes driven busines and 10-15 seats is not an economically viable option for long run. You nede atleast 50-60 seats to break-even in 12-18 months.
Hardware and software vary with applications that you will be servicing and can wither be bought or rented (through an ASP option, very popular in Europe now).
Do write in in case you need any more info.
Cheers, Manoj Matai.