Just use the Internet. I went onto two different company Web sites--Proctor & Gamble and Kimberly Clark (which was co-founded by one of the men who built the house in my avatar). Everyone has information up for investors and future employees--plus you can also request information if they have a place to do so.
Corporate organization: That seems hard to get--I'm guessing because org charts aren't very interesting things except to the organization. But you may be able to ask about one from a company.
Job Structure: Well, I think the first thing you need to decide is if the company is going to be a large business or a small business. This makes a huge difference. I've worked for small companies previously. Both had about 50 employees. The first had a company owner, chief executive officer, chief financial officer, a human resources person, chief technical writer, and about three or four project managers (there's an orientation book on project managers; might be helpful in creating your character). The second company had an owner, chief executive officer, and they were having a lot of trouble recruiting project managers. I ended up direct reporting to the CEO, because no one was in charge of our project.
A smaller company will tend to be more consolidated--though that depends on the area. I'm in the Washington, DC area, so any company is likely to automatically be in two states and the District and probably do work for the Federal Government. A large company like Lockheed will have locations all over the United States.
What the company also does is important. That would influence the corporate structure (a retail chain is more likely to have areas focused primarily on retail; whereas some place like Lockheed might have huge government contracts that are managed by project managers). Once you know the industry, then you can do research in that area--really, like a job hunter.
Also decide on locality. I researched my great-great grandfather for genealogy purposes, and there's a lot of information on him and the company in the local newspapers. Unless it's in Washington, DC (where they only talk about politics), you may be able to find news relating to the company.
The library will also have tons of business books. Most will be on leadership, but you'll be able to pick up stories from CEOs on how companies run--and often, how they run badly. Business books are a very popular subject. Federal Computer Weekly and Government Computer News (both online publications that you can look at) will talk about businesses in relation to working with the Federal Government.