When hiring a contractor, always, always, always check their license with the state licensing board! You never know what you will find! It can save you a ton of cash. This simple rule has helped me avoid more problems that I can count.
I do a lot of contractor hiring in Colorado and Florida. So I make extensive use of these two sites:
This goes for hiring roofers, plumbers, hvac contractors, electrical services, pool contractors, and even home inspectors. All of these are licensed by the state. Even they’ve had complaints against them, the complaints will be listed on these sites.
When researching contractors, the biggest issue I seem to find is old permitting fines. This means they likely got caught doing a job without pulling a permit for it. And whenever I see problems with contractors not pulling permits, I run from them. If they’ll cut corners on the simplest parts of the job, there is no telling what they are doing within the walls and attic of your home! So, just make sure you do your due diligence before hiring your contractors.