At Field Mag, Andrew Szeto explains the fundamentals of building a basic A-Frame cabin. He writes that you can get it done for about $8,000, not including land.
The most major lesson learned is I should have gone bigger. Don't get me wrong, the cabin is awesome, but heck, an extra 5-10 feet in both directions would have been a game changer and made it a little more habitable. But to see a thing you built come to life is the greatest gift you can give yourself in my opinion.
A strong theme is not to go cheap on materials: don't use thin plywood for the interior, don't use polycarbonate roofing, don't build without properly levelling the land under it.