And with just a little more data you can actually determine how many customers you would need for each year you plan for and how many leads you would need. From that you can actually determine what size market you would need and whether your market is big enough to supply those leads that could be converted into customers.
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.