It does not have to be long or overly complicated. It simply has to have the elements required to put your goals into action. Developing a SWOT analysis (strengths, weaknesses, opportunities, threats) will help you to identify problems before they start. Craft your own or hire a business writer to create a dynamic plan that will guide your operations. An effective plan is one of the most important elements over overall business forecasting.
So if you can put this all together, you can have a complete business operating plan that would show you exactly what your business would need to do to give you the income and profit you would like to have and a rough idea whether your market would support it or not. All you would have left to do would be to figure out how to make it all happen.