I suggest that you construct easy to read tables and graphs for the financial portion of the plan. The worksheets suggested are: Salaries/Wages and Benefits, Outside Services, Insurance, Advertising Budget, Occupancy Expense, Sales Forecasts, Cost of Projected Product Units, Fixed Assets, Growth (or Start_Up) Expenses, and Miscellaneous Expenses. You may find some of the worksheet templates at PlanWare.org to be useful.
The financial statements section should show the way things are now if you have an existing business, as well as a forward look at your checking account, or projected income statement. The only way a start_up company can provide an income statement and balance sheet is by projecting these figures based upon well defined assumptions. Both start_ups and existing businesses should include a statement of owner's equity.
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.
The main thing to remember in this section is not to provide new data, but to explain in detail data that has already been provided and to provide the support for that data.