Licensing information from Michigan.gov
You should be aware that all contractors offering to do work which totals $600 or more in labor and materials must be licensed by the Department of Licensing and Regulatory Affairs.
A Residential Builders license allows a contractor to build a complete residential structure and to do maintenance & alteration (remodeling) work on a residential structure.
A Maintenance & Alteration license indicates that the holder has met requirements for one or more of the following trades:
Screen and storm sash
Tile and marble
The trades for which a maintenance & alteration contractor is qualified to practice are listed on the license.
The holders state license must be displayed in the place of business and all contractors and their salespersons must carry a pocket card which you should ask to see.
If they cannot show you a license, check the department's License Information database or call the Licensing Division at 517-373-8068.