The business plan you write will need to include overhead estimates, or at least a list of the regular expenses of running a laundromat. These will include machine maintanence, janitorial supplies & labor, stocking and maintanence on coin machines and laundry supply dispensers, rent (plus NNN), electricity, water and gas, and internet/cable if you choose to provide these.
You will also want to estimate how many people can use your facility in a day, doing how many loads of washing and drying. Also, think about what services your facility might provide like dry cleaning or "fluff and fold", etc. How much revenue can these services generate?
Location should be part of your plan as well as your ideas about where you will draw funding or how you will cover the costs of the start-up.
A plan should be as specific as you can make it, but will always be list of goals and estimates in the end.