The planning wizard makes it a snap to get started since you simply answer yes or no questions to create your custom business plan framework. Bplans.com offers free business plan samples and how-to articles as well as a wealth of other information. It is definitely worth taking the time to checkout. Microsoft Office Online Templates also has a variety of free templates to use with their products. The wizard indicates the information you need and you fill it in as you go.
You may find that the easiest part is the actual writing of the plan. The real work comes in the data-gathering, which may take you a hundred hours or more, depending on what you already know or have researched. If your new venture is in an area where you've been working, you may already know about your customers, your suppliers, your marketing plan, your organizational structure, your financial and cash flow needs, equipment, inventory, and so on.
U.S. Census Bureau (census.gov): A source for a variety of useful statistics, especially the Economic Census that comes out every 5 years.
Besides, your friends may be 100% behind you in your new venture, but, in case you are hoping to involve others who have actual money to invest, you may need to be able to make a convincing case. Wouldn't it be nice to have anticipated possible questions and be ready with plausible answers? If you are risking your own money, that is perhaps even a stronger reason to do some indispensable planning.