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.
But your fixed expenses don't do this. They remain the same no matter what sales does. That's why it's call fixed. These are expenses like rent, taxes, utilities, phone, salaries, insurance, etc. A lot of business owners never consider this. They just lump all their expenses together. But you could never make an accurate plan if you combine all your expenses together. If you project your sales higher and want to know what your expenses will be, you have to separate your fixed and variable. So, thinking about this principle, let me ask you a question. If your sales grew 10% and nothing else changed, would your profit margin be higher, the same, or less? Profit margin is % of profit against sales