building a pole shed
 

I have been thinking about building a pole shed for a few years, and I
think next year is the time to start. can somone point out some things
I need to research on this? this is a start of some of the issues I am
looking at

40x40 shed in northern wisconsin
as cheap as possible, I've been looking at recycling from other
buildings for materials (freecycle.org and cragslist free areas)
use sonotube for forming pole footings
fill to level
2 inches of ground insulation (does it have to be a specific
insulation?) for frost to extend outwards 4 feet from floor of the
shed
how many inches of sand for burying tubing for future in-floor heat
rafters or roof trusses? build myself or buy (building at zero cost
is a plus)
does NOT have to be a clear span, 20x80 would be the same sq ft, but I
dont have the foot print for such

I am possibly considering builing it in 4 sections, 10x40 to help
store additional shed materials and to make builing it easier.

I plan on hopefully pouring a floor for it in the late future, should
I worry about the sand and radiant tubing now or then?