It sounds like we went further on the DIY end of the scale than you're talking about, DMY0013, doing the foundation dig, prep for slab including gravel, rebar, and insulation, but not the pour (slab and three walls), then absolutely everything else, framing, electrical, plumbing, roofing, up to the drywall which we hired out to get into the place faster at the end. Oh, we did hire someone else with a ditch witch to run the main water line up to the site (a quarter of a mile, not a hand-digging job) and to put in the septic tank.
The finishing still isn't done, and the siding isn't quite done either, after almost a year and a half in the house. From breaking ground to moving in was almost exactly three years. (We lived on site in a mobile home that could most kindly be described as "vintage.")
It all takes a lot of time. We didn't really have the trouble with subcontractors Spork is talking about, but then we only hired three (water/septic, concrete, and drywall) and the septic guy and the drywall guy were people we knew; the drywall guys are good friends. So we got lucky with the concrete folks showing up, and we had the estimates in writing.
But Spork and I both live in warm places, and, I think, in places with less stringent codes and inspections than I imagine you may have. Both of those are likely to change things. Hopefully someone else will have some insights in to Canada or at least the northern US.