OP,
Building on greenrvgreen's comments above, I think a realistic assessment should be done on it's expected value if you have to sell. I believe you mentioned that you'll be in Washington for a few years, then possibly move up to Alaska.
Have you considered just getting a used park model for now, selling it when you need to move, and then when you have a better idea of where you'll be permanently located, buy something there? I know it won't be quite the layout you want, but it will get you housing cheaper and probably be easier to sell as well. This will only be "short term".
I think this is a neat project, but I'm not sold on the idea this will have much value to most people, may not be allowed in some campgrounds and wonder what it might cost you to have it towed from Washington to Alaska if you don't have access to a very large truck.
Now if you're building it and don't expect to sell it and have the means to safely move it, that would be different.
Again, good luck. I hope it all works out for you. :)
~Rick