For Washington State, it really depends on where you are. If you are located in King County, it will be a long hard fought battle of paperwork, presentations and inspections to get open. It is one of the most business hating counties in the state. However, if you come under the city limits, they you may have a better chance.
Check your location and go to the appropriate agency (city or county planning). They should have a zoning map and if you are in a residential area, you will need to get a variance. That is hard work, tons of paper and going to planning meetings.
Oh ... and anyone that tells you that you need paved parking, just ask them to show you the requirements so you can make sure you are following all the rules. You may just find that he/she was just blowing smoke.
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