As long as you are 18 years and over and have a clean criminal record then you qualify for a private investigation career. There are no formal education requirements for most private detective and investigator jobs, although many private detectives have college degrees or have taken legal or criminal investigation courses.
In the US, most states require P.I.'s to be licensed however, it may pay to check with your state's governing body on the requirements as far as licenses are concerned in your state.
While there are no formal education requirements for entering the private investigation business it might pay to take a course particularly if you lack any qualifications in other areas. It's interesting to note some schools and colleges are starting to offer courses in the P.I. business as part of their curriculum.
Insurance companies, banks, law firms and most corporations use investigators in some form or another.The average freelance investigator earned around $4o,000 in 2008.