How difficult would it be to build a one room plus bathroom house?
The actual process of construction, I can get the ingredients.

I'm thinking of buying a gardening lot and building a house that can pass for a large patio/shed when it comes to inspections.

Hardest part would be laying cables and the plumbing right? I would also need either a plate furnace or a fireplace, either way I need a chimney that doesn't let heat out.