I'm building my forever custom home right now and am doing a lot of the stuff mentioned here. But the most important thing to me that I don't think has been mentioned is just make sure you build it IN THE RIGHT PLACE. I had an awesome house in the wrong county (away from family, I like my family). My last house had a sweet metal shop, barn with nice tack room, great deer hunting, concrete storm shelter, quarter mile away from the road. It was great but it wasn't home. Was sort of the plan from the beginning but market got crazy, did some cosmetic upgrades and sold it for almost double what I paid to some guy in the city. Worked out great for both of us. Now I've got a nice piece of land on the farm I grew up on with great potential for deer, turkey, waterfowl, squirrel, and bird hunting and my kids get to grow up with their family, hunt their own land, and learn the value of work and taking care of something important. I could be happy with a nice trailer there because it's the perfect place. Don't build the perfect house in the wrong place. Find the perfect place then do what you need to live there.
For some actual tips on building here's what was important to me. Extra steel and concrete in your footer, cheapest insurance you'll ever buy. Standing seam metal roof, never have to do it again. Spray foam insulation with unvented crawlspace and attic or do ICFs as others have mentioned, ICFs are the bomb if your house plan makes sense with it. Don't cheap out on windows. My garage is on the low side of my house so I dropped the 2nd level floor system in it and made it a huge man cave, try and use that space if you can. If you do porches, fill under them with rock instead of a floating slab. If it's a crawlspace, add an extra layer of block. I like the home run pex plumbing because it's the fewest connections and you can place the manifold in a convenient place and have shutoff valves to everything in one spot. Plan for a good security / camera system. There's probably more I'll think of later but hope this helps someone.
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