While these are easily available online, some of them are way better than the others. A lot depends on the approach that goes into writing the business plan.
U.S. Census Bureau (census.gov): A source for a variety of useful statistics, especially the Economic Census that comes out every 5 years.
Production Operation - If a product must be manufactured, what is the process? Will the work be done on-site or subcontracted? Who are the subcontractor(s)? If on-site, what space, equipment, machinery, production employees are needed? What suppliers are needed? Who are they? How will quality be assured? What is the anticipated production output? What established credit lines do you have? Possible Data Sources: local Chamber of Commerce; yellow pages; trade associations.
"Plans are useless; planning is indispensable," according to Dwight D. Eisenhower, then Commander of the Allied Forces in Europe during WWII. Now, you may be in total agreement with the first part of that statement, but you are really not convinced of the truth of the second part.