We did this on a smaller scale (30 * 40) a few years ago and included a small full bath and septic dump for our TT. We built it before our house (and lived in the TT inside it for 4 months while finishing the house) so it includes the well pump. The county allowed us to add a second septic tank behind it with a pump that goes to our main septic tank. We figure it will be at least 10 years before it needs to be pumped out.
I could not talk them into allowing us to include a drain in the floor. We were also told that no one could stay in it after we got house occupancy permission.
It is open with exception of the bathroom. Include some 220 volt outlets. I use them for a 220 volt space heater that can be put where it’s needed. I also later added a 220 volt ac window unit thru the wall that won’t cool the whole place but does knock the temperature and humidity down to tolerable levels.
