You may look at a piece of land and see things you like, but having an actual check list will help you evaluate things most clearly. Apply points to them based on your priorities.
Due Diligence is very important. Have a local design-builder go with you. They want to help you cost out your project and help you avoid issues you may not even be aware of.
Common Issues to Consider When Buying Land in Oregon and Washington
Planning: A beautiful lot is not always a buildable lot. You must research what restrictions are on the land from the county, town, or neighborhood/short plat CCR’s. Are there utility or “neighbor's access” easements through the center of the lot that the seller is not making clear (or even aware of)? Is there a seasonal stream/creek that you can’t build less than 100 feet from? You might not see one if you are looking at lots in August.
Wind: If you’re from out of town you will need to get local knowledge on this topic. Wind changes depending on time of year and can ruin your outdoor living if you have not accounted for it in your design.
Sun: Same as wind. West facing afternoons can be extremely hot, if your view is west do you have proper shade in your design? How much south facing (desireable) view do you have?
Rain: It rains and drizzles in the PNW, but it’s not super cold. You can enjoy your outdoor space and barbeque year round if you have proper eaves and covered porches in your design.
Light: Is the property on an outside corner of an adjacent road? If so, headlights will spray across your house at all hours. Neighbors often put bright lights opposite their bedrooms, or on their garages inadvertently causing light pollution onto your property. Think about how to shield yourself from that annoyance with the designer.
Noise: You may be visiting a lot when the trains aren’t going by, or the golf course blowers aren’t in use, or the neighbors' range animals are not around. Local knowledge is key here.
Utilities: What comes on the lot? Power, Water, Septic/sewer, cable, natural gas. All these things have associated costs. Many soils are inadequate for a standard gravity drain field, and if so can add up to $60+k to the cost of the lot. If you need a well, that could be $20-80k. If underground power is required and your lot is rocky, you could be paying $60+ per linear foot to trench, add conduit and rebury with gravel.
Access: How will you actually get to the house? Look at driveway length, slope, width, turning radius, shared roads, private road agreements, and emergency vehicle access. A steep or long driveway can add substantial excavation, retaining, paving, drainage, and maintenance costs. In some locations, fire department access requirements can also influence where you can build.
Also consider snow removal depending on where in the PNW you're targeting.
Steepness - lots are the most challenging (expensive) to build on and can have the best rewards design wise. If your designer work is in 3D and has the topography, you have the best chance to avoid costly mistakes
Rocky lots are expensive to build on as mentioned above for utilities, but also driveways and foundations, but can have huge rewards for landscaping which your designer would help you evaluate.
A Challenging Property can Produce an Interesting Home
Some of the most challenging properties can also produce the most interesting homes. A steep lot may provide incredible views. Existing rock formations can become part of the landscape. An unusual orientation may lead to a more creative floor plan.
The goal of due diligence isn't simply to find reasons not to buy a property. It's to understand what the property will require before you buy it, so the land, home design, construction budget, and lifestyle all work together.
You will need to have a capable land-use planner help you in many cases. A design-build firm with a planner on staff is helpful in these situations.