In any and every state there is the at hand resource of the BBB, Better Business Bureau.
And in our technology age one can simply google any company and place the fear they have following their name (xyz contracting rip off, bad reviews) and see what comes up. In a case like that, the absence of evidence is generally the evidence of absence.
Next level would be the licensing body in your jurisdiction. Some states licenses contractors, in other states it’s the county or city. Find out whom issues contractors licenses and call them and ask - they will have the full records.
Last advice I would have is more my personal insight, and that is trust your gut. If you’re considering doing business with a person and your gut has such a negative feel to it, on in which you would feel the need to contact licensing boards and in depth searches to over-ride that “bad feeling”, well I just wouldn’t do business with someone. I would at least want to start with a service provider I felt great about, and do some simple verifying of that “good” feeling.