How can I know if my contractor has complaints or lawsuits against him?

Working with Contractors Evaluating Contractors
2

Casey, check the Better Business Bureau, Angies List or similar, major search engines online, your contractors licensing agent (if applicable)

You should search the contractor by first and last name and Business name and license information separately for maximum results

Good luck

3

Check with your local contractors board. The BBB is also a good place to look. Yelp is another good place to look for reviews.
Hope this helps.