Smaller businesses are not required to reveal information about themselves and are often reluctant to do so. But if you have worked for an existing business or have a relative who owns a small business you may get useful and realistic information about what it takes to run the business. Remember that you want start-up information and the owner or manager you interview may be a little hazy about past events. Occasionally, they describe a case study in sufficient detail for you to figure out what happened in the business. Probably more useful are trade magazines.
Every industry has at least one.
The library often carries them. Financial statistical services. They give valuable information about typical relationships, for example of sales to assets that will help make your business plan realistic. The latest issues are available at the reference desk on the main floor of the DuBois Library. If unavailable, earlier versions are available in the reference stacks and should do as well.