The Growth Management Act shapes everything rural
Washington requires counties to plan for growth by designating urban growth areas and protecting resource lands outside them. The practical effect on a rural land buyer is that development rights depend on the county's designation of the parcel, and designations for agricultural, forest and mineral resource land carry real restrictions.
Establish the comprehensive plan designation and the zoning, then ask the county planning department directly what residential development the parcel supports. Do not infer buildability from acreage.
Water availability is a live question
The permit-exempt well has long been the route to water on rural Washington property, and the Hirst litigation and subsequent legislation made clear that this route is not unconditional. Basin-specific instream flow rules, closed basins and county requirements all bear on whether a new well can legally serve a new home.
Before buying build-intent rural land, ask the county whether a building permit relying on a permit-exempt well would be approved for this parcel, and check the water resource inventory area rules. Our water rights guide explains the underlying doctrine.
Critical areas reduce buildable ground
County critical area ordinances impose buffers around wetlands, streams and steep slopes, and those buffers can consume a large share of a parcel. Western Washington parcels in particular frequently carry wetland and stream buffers that leave far less usable ground than the acreage suggests.
Where building is intended, identify the critical areas and their buffers before valuing the parcel.
What to verify
Comprehensive plan designation and zoning. Water availability for a permit-exempt well, confirmed with the county. Critical area mapping and buffers. Legal access and septic feasibility. Then the risk scorecard.