It is usually recommended that these projected statements be on a monthly basis for at least the first twelve months or until the business is projected to be profitable and stable. Activity displayed beyond the monthly detail may be in summary form (such as quarterly or annually). The forecast period for most business plans is two to four years.
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.
Explain the fundamentals of the proposed business: What will your product be? Who will your customers be? Who are the owners? What do you think the future holds for your business and your industry?
You may not have thought much about your competition or outsourcing some of your work, but things like that will impact your ability to make a profit. And you will find this especially so in the beginning phases of your business. Even you are just opening a lemonade stand in the front yard, you will still need to know what Susie is selling her lemonade for on the next street over!