How do you know if you're choosing the right company/contractor for mold situations?

Please advise!

Mold identification and abatement, or a building contractor who can fix the cause?
If you haven't fixed the cause, I would do that first.
Contractors in some areas measure the area of mold and tell you that by code, only an abatement company can handle it. Others are happy to just rip it all out themselves.

Most mold is not hazardous to humans e.g. penicillin. Why are you concerned and what is the issue? Did someone try to scare you into providing mold removal?

CDC - Mold - General Information - Basic Facts

Mold Removal, How to Kill Mold with Bleach, Borax, Vinegar