General Liability insurance is the absolute first step. They have to SHOW YOU, and then you have to call and confirm that the policy is valid.
GC license in my state often means a higher price point, BUT if you're permitting or dealing with code, then ABSOLUTELY, get the license creds and then call to verify.
Make them sign a Lein Waiver before collecting final payment.
Really, this business is full of both good people and bad. Things should proceed exactly how you two agree that they will. Your vendor should be available and communicative. If not, they shouldn't be hired.
People flake out, and we all have made errors in judgement. Just be ready and act quickly. All of the pro's I've used have NEVER:
1. Needed cash from me to afford materials.
2. Needed special consideration (like doing the work after another job, etc)
3. Broken their word on pricing guarantees. When the pricing changes, they tell me why and give me the choice.
4. Missed a deadline and just hoped I wouldn't notice.
If any of the above happens, they're done with me...forever. And I make that expectation clear.
We all get hosed from bad people, it happens. Trust your gut, and your brain. Do not surrender your dominance, and for the love of all that is good in this world, leave emotion out of it.