You may remember this Iowa company which has done something similar, using their prefab metal buildings for emergency housing, at roughly the same price:
https://www.sukup.com/Buildings/144/Safe-T-Home
My parents wanted to be able to visit where they grew up so they purchased 7 acres in a rural area. They planned to eventually build a house there.
Daddy decided to build a cabin so they could spend a few days visiting relatives, then go back home. Daddy and I built everything except the septic tank. The exterior and interior were 8X10 pieces of plywood.
I would guess around 15x25 feet. The bathroom was small with only a shower, no tub. It was basically one open room, very sturdy but plenty of room for them and if I wanted to use it too but not for both. After a year we added on a laundry room so they could stay longer.
If a person had to just survive in that cabin it would have been fine. Also had a sink, small refrigerator and stove. Also two nice windows.