An immigration business plan is a business presentation using the business plan format and written to conform to the requirements of a visa application.
The content of the document matters as much as the content goes into your visa application. It is meant for the immigration officer who needs to decide if your case is legitimate and if it is in line with the visa you are applying for.
Except for the EB5 project, there is little consideration given to whether your business is worth the investment. The document is predominantly centered around US business immigration.