” “What is the geographic area for the nonprofit’s services?
It's a "plan" after all - and the underlying assumptions may change.
If they do, then having a plan can be useful during the process of identfying adjustments that need to be made to respond to changes in the nonprofit's operating environment. A business plan prepared for a bank (to support a loan application) may be different from a busines plan that board members will use to help define their priorities in recruiting new board members.
The plan may include details about the need for the organization's services (a needs assessment) and about the likelihood that certain funding will be available (a feasibility study) or about changes to the organization's technology or staffing that will be needed in order to successfully advance its mission.
Another potential aspect of a business plan could be a "competitive analysis" describing what other entities may be providing similar services in the nonprofit's service and mission areas.