Were I you, I would contact the local police and see if they can direct you to whoever licenses PIs. Once you've located the licensing board, you can get all the info you need from them. And it may be that the police license PIs. If not them, it's likely one or the city department. Requirements vary from state to state, so without talking to a PI, it's a bit hard to know what the particular requirements are in your area.
Here is the link to the state of Wisconsin PI license info -
Here is the link to the Wisconsin PI association web site -
Hope this helps.
You need to take a state cource and have an apprentanceship under one
Most states require prior law enforcement experience, or much work with a licensed PI. At this writing only Utah has no such requirements, IN UTAH YOU MAY JUST APPLY.
Its vary by state. Collect information about criteria in your state, for example In California it takes 6,000 hours, or about 3 years fulltime work, under a licensed investigator to be eligible to take the state-issued exam.
Private Investigator http://www.osi.com.ph/
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them