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.
Business plans are mostly about organizing, formalizing, and committing to a specific plan_of_actions. Such a document generally presents the objectives, strategies, analysis, and a detailed roadmap for implementation. Underlying a plan_of_action is comprehensive analysis of historic, current and proposed results all supported with assumptions. If anyone doubts the interest in business plans, a Google search returns more than 62 million and Amazon list more than 77꺜 titles concerning this subject.