Three of my four kids are more than half-way interested in tiny houses based on Conex shipping containers. It is probably because Mrs ERJ read The Boxcar Children series to my kids when they were wee tykes.
Working the math, two 8'X40' Conex containers run about $4500. A 24'X41' portable carport to shade them and protect them from precipitation runs about about another $4000.
In gross numbers that gives you interior space for $13.50 a square foot.
The exterior walls and ceiling need stud walls, insulation and drywall. Windows and doors need to be Saws-alled into the sides and installed. A hotplate and sink are enough for a kitchen. Add a composting toilet, a small LP heater vented to outside and a window air conditioner and you are living high on the hog.
You would want to wire for 60 Amp service and you need accommodations for grey water.
|Source of image|
Of course it is not a residential space. It would never meet code. It is a work-shop with a futon and a few amenities.
If you want a really tiny "shop" you can shrink down to an 8'-by-20' exterior shell but the price does not scale down proportionately.
Technically, there is absolutely nothing difficult about converting a Conex container into housing. It might even be the most effective way to deal with homelessness. The trick is finding somebody who is willing to let you park your "shop" on their property.