At my previous home I had a ~30 X 50 building with concrete floor that I
used for my home shop. Moved to the country maybe 5 years ago and don't
have a shop building or garage, just a car port and a wooden storage
building.

I'm trying to come up with the most cost effective home shop building I can.
I don't want to have to depend on any income from the home shop but I think
I can get some business if I get my shop set up. Part of my motivation is
that my son is now 11 and I'd like to teach him machining, controls, and
automation. The con is that every dollar I put into a shop is a dollar not
paying off something else, but may be dollars well spent (perhaps my shop
building would pay for itself and give my son some valuable experience).

So what type of building is most cost effective? (All metal, pole barn with
metal or wood skin, or ?) Would anything (wood, metal?) be good for a
smaller building for now but be expandable later if I needed more room? I
assume I need a concrete floor for the machines (I have 3 mills and 2
lathes, plus a press, welders, saw, and wood shop tools) would it be
advisable to save money with a part concrete, part rock floor?

RogerN