Other than a recreational vehicle in a recreational vehicle park, the only allowed use of a commercial coach or recreational vehicle is as a temporary office for a period of time not to exceed one hundred twenty (120) days in duration in specific instances where a permanent structure housing an existing licensed business has been destroyed or damaged to the extent that it is rendered unusable. The sitting of temporary structures shall be approved by the Building Official and shall not require site plan review in conformance with Chapter 19.49. Temporary structures shall maintain a twenty foot (20') separation from property lines and/or other buildings or structures.