Sizing a garage or RV barn
Measure the length and height of your RV or tallest vehicle, including any roof air conditioner or antenna, and plan door height and width with clearance. Think about where you will turn in from the driveway, too. A slightly bigger building usually costs less than a second one later.
Neighborhood lots vs. acreage
On a city or suburban lot in Spokane or Spokane Valley, setbacks, height limits and any HOA rules shape what you can build. On acreage out toward Nine Mile Falls, Cheney or Otis Orchards you may have more room, but access and site prep matter more. Either way, check zoning before you settle on a size. See pole barn permits in Spokane.