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.
Organization - How is the business structured? Who are the principals and the principal shareholders? What authority does each principal have in the venture? What are management's qualifications? What is the job description for each position? What does the organizational chart look like? Possible Data Sources: on-line templates for job descriptions & organizational chart.
This may be nothing more than arranging training for employees or setting a timeline for goals to be met. It is not unusual, however, to find them becoming a temporary presence in different office activities.
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.