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.
If you are one who is intimidated by the blank page, never fear! There are several good software packages that will guide you through the process, such as Business Plan Pro Complete from PaloAltoSoftware. Business Plan Pro Complete walks you through the entire planning process and generates a complete, professional and ready to distribute plan with a proven formula for success. 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.