The rule is "related business expenses".
Examples: A room converted into an office devoted to running your business. Proportionately tax deductible calculating from total rental paid or the depreciation of your house.
Gas to deliver your product or meet the client. Again, proportionate cost in depreciation if you are using your car for your business.
I don't know how campground fees can be deductible since land is already part of a lease rental in an alternative scenario that you are renting an office or a factory for production.
