When making a business case for a project, some of the items to include are listed below.
Executive Summary is a short description of what the intent of the endeavor is.
Operational plan lists how the business will be run. For instance if you are building an online cloud computing business similar to Amazon Web services, the operational plan will list the details about how to hire individuals, the location of the business and so on.
Scale and complexity assessment lists at what scale the business will operate. For instance, how many data centers will be setup. What will the growth of the scale look like in year one, three and five.
Financial analysis is one of the most important aspects of the business plan. This will list the ROI, or return on investment, which is a key driving factor in making a decision on whether to find the business or not.
Project plan is a subset of a business plan. A project plan is for a specific purpose and a specific time. A business plan might refer to various project plans that drive the business.