A company's structure impacts the information that can be found about it. When choosing companies to research, test-search first to determine structure and the whether the amount of information available will be enough for your needs.
Parent or subsidiary company?
Public or private company?
Additional tips for researching companies:
Public companies are required by law to openly share some of their financial and business records. Annual reports are an especially useful source of this information. These are also known as 10-K reports. (Private companies do not provide annual reports to the public.)
Two places to find them:
This tutorial was created by business librarians at the New York Public Library.