Mich. Comp. Laws § 338.825

Sec. 5. (1) The department, upon application and after making a determination that the applicant is qualified, shall issue the applicant a license to conduct business as a professional investigator for a period of 3 years from date of issuance. (2) Upon the issuance of a license under this act to conduct business as a professional investigator, the applicant is not required to obtain any other license from any municipality or political subdivision of this state.