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.
Another key element to the marketing section of your business plan is an outline of your marketing objectives, strategies, and tactics. Writing down the avenues you travel in order to market your business will afford you the opportunity to record what worked and what didn't work. You must be able to measure and calculate the results of your marketing efforts, otherwise, what's the point? If you don't know if something is working for or against you, then it's working against you.
If an online business, you need to go into detail how you will attract customers to your website. General statements like "I will use Face Book ads and email marketing" will contribute almost nothing to helping your cause unless you have detailed statistical analysis of tests you have conducted or of another similar business you have been associated with. If you do not have any data upon which you reference your estimates, it could show lack of proper thought to the remainder of your business plan.
The three basic actions for growing a business in any economic climate are: improve efficiency (maintain output while reducing inputs, such as time and money); increase volume (produce more in order to spread fixed costs); reorganize the business (change goals, methods and/or philosophy). If you plan to implement one of these, you may as well plan to implement them all. By focusing on one of the above strategies, you will find a ripple effect that causes a need to address the others. This is a good thing.