For becoming a private investigator there is not special license provided by Government of India , Hence your undergraduate degree is taken as your qualification. You should have a undergraduate degree in any field.

Also there are not many Institutes in India which offer this course , if you are really confident of doing an course in Investigation here are a list of few colleges given below:

1. The Indore Christian College, Indore
2. The National Institute of Private Investigation, New Delhi

There are also many private Detective Agencies that provide you certification course in this field

1.ACE Detectives India International Securities in New Delhi

2.All-India Private Detectives Association in New Delhi.

3.Lancers Network Limited in New Delhi.

You can either work in domestic issues or corporate related cases  but how quickly and efficiently you solve the case matters .

Thank you , Hope it helps

Candidates who want to become a detective you need to complete your graduation in any discipline. Then only they can pursue private detective course in any reputed institute or detective agency. After completing this course, they will become eligible to apply for job in any reputed detective agency.

Hope this helps!!

All the best!!