haha I'm not sure. Definitely not trying to stop him from doing it. I would love to do something similar but my wife would never go for it! I had some idea that VT had very strict laws about percolating and you pretty much had to have a septic system no matter what but there must be exceptions with the camps because they are all over the place. But I have no concrete knowledge, just hear say. I know up on Sugarbush at Allyn's lodge they have "indoor" outhouses. What constitutes indoor plumbing? I'd want to have a sink with running water myself.
I know that Yestermorrow design/build school will sell you a small yurt for 1000 bucks. I think you could build a "tiny home" frame and roof for not much more and be a lot more comfortable.
Search for kirstendirksen on youtube ,she has 100s of videos of interviews with people who live in small homes/alternative living situations, etc.
I always like the container homes too. It's like 2K for a almost new 20x8 container, not much more for a 40x8.
good luck!