If you develop a good Profit & Loss Statement for your existing business for the current year or for the first year of your proposed business, you can use this data to actually project how much sales you would need to yield the income you want and the profit margin you want. You can plan ahead as far as you want. Sound impossible? It's actually pretty simple and can be pretty accurate plan.
Here is a recap of where we are in this discussion: Business plans formalize an understanding of the task with appropriate analysis leading to a plan_of_action. Not all business plans are for profit motives. Business plans are for an enterprise effort and not focused on disciplines/departments, e.g. Marketing plan, sales plan, HR plan, supply chain plan, etc. Business plans are a great vehicle to build a team effort. Plans can be utilized for formalizing metrics relative to achieving goals and performance measurements. Some complex plans might include a Project Management professional. There are internal and external audiences for business plans. Most external focused plans are for outside funding of projects. Be mindful of the 'tone' the plan projects to the reader. Tone refers to the impression a person gets from reading the plan; a subliminal feeling about the plan.