The internet is a fantastic resource for writing a business plan, but for some people, nothing beats a good old-fashioned book. Your local library has entire sections dedicated to the multiple aspects of business development, and you can be sure to find several books about how to write a business plan. Best of all - these are free! If your local branch does not have the book you're looking for, check the catalog and request a book transfer. Sometimes, the perfect books about writing an effective business plan or ideas for a sample business plan are just an inter-library loan away.
Since your mission statement is only a few pages long, your executive summary will allow you to further expand upon key points mentioned in the mission statement. Consider including your business history, biographies of key players, an overview of the business including locations, employees and available products and services. You can also discuss goals and future plans. Use this section to really draw in the readers.