I totally agree with what Amit Naagar said. First of all its better to gather some knowledge and also experience before making it a business.
Both domestic and international have their own set of rules for work and hence the requirements. A call center is not mere managing some employees sitting in and out of your office but to retain them as well. I think if I am not wrong BPO industry has very high attrition rate and to keep the process retained, you must have to keep enough manpower ready in buffer incase of emergency.
Hope you all who are willing to make it a business take all the details regarding it, the pros and cons before finalizing