So, although a detailed business plan may not be required for an online business, I am going to include it here so you can at least look at and consider each section and determine yourself if it applies to your business.
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.