A business plan contains several main elements. First, it lays out the mission and the goal of the business. The plan will spell out whether your company is in business to serve a greater good or simply to fulfill an unmet need. Determine whether your business will serve other businesses or supply products to consumers. These are all important elements that should be included.
Do not try to write your business plan in one sitting. As I mentioned in the beginning, for a traditional brick and mortar business, it could take in excess of 100 hours to compile all of the information needed into a comprehensive but yet understandable document. For online businesses, probably not that long. But your final product should be well thought out, well documented and easily understandable.