>>2853450Enthusiastic, you'll learn a lot if nothing else. As has been mentioned previously, you're going to want a wood floor, and you'll want to airgap it between the earth fill you use underneath. That will be the single biggest thing you can do for livability, after CHINKING. You're creating a big headache for yourself with those gaps, you'll want to chink the everloving hell out of that to make it reasonably comfortable. Once it's built and you've spent time living in it you'll see what you like and what you don't, and you can go for round 2.
You should seriously consider
>>2853076 for a number of reasons. Stealth is not so important, but the big thing is climate regulation. In the hot summer it will be cool thanks to the earth surrounding it, in the winter it will be warmer, thanks to the earth surrounding it. It will also be shockingly quiet, even in a big storm. You can make life easy by wrapping that cunt in pond liner before reburying it, and working out a french drain for the unit proper. You've clearly got grade enough on the land.
But that's a future issue. Get it built, get it lived in, save up some capital, then go for round 2. It's a good project.