Do not even think about hiring a mold remediation company that can’t provide documentation of their liability insurance. These companies must actually carry a special form of this insurance, known as environmental pollution insurance. It is required by most- if not all- state governments. If the company you’re thinking of hiring doesn’t have it, they are operating at least somewhat illegally. Not to mention the fact that you’re taking a big risk. In other words, if they damage something in your home, it may not be covered under the contract.
It’s not unusual for a company to provide both testing and mold remediation, but it’s bad form for a company to offer both to the same customer. The reason is obvious. It’s a conflict of interest. Of course, a mechanic doesn’t consider it a conflict of interest to both diagnose a problem with your car and then charge you a fortune to fix it, but that’s the world we live in. In any event, you’re better off dealing with two separate companies (assuming that you didn’t detect the growth yourself). If you are comfortable with the mold remediation company after they’ve performed their service, you may feel okay about having them back to test in the future.
It’s not unusual for a mold remediation company to make use of subcontractors to perform the actual work. There’s nothing specifically wrong with this, but everything should be above board. In other words, if you’ve invested your time and resources into making sure the company has a good reputation, is properly licensed and insured, and won’t mess up the job, all of that is out the window once subcontractors enter the picture. Make sure the people you hire are actually the people who will be doing the work.