You're definitely right that there are no certainties in life!
As you said, the best you can do is make a rational decision based on the plans that you do have. It's a difficult balancing act to buy a property that's future-proofed (against whatever you think that future might be). My point is, today, in Calgary, I would hesitate to buy a place unless I could reasonably think of it suiting my lifestyle for at least the next 5 (if not 10) years. At that point, the intangibles carry enough weight to balance or offset the financial uncertainty (IMO). If there's a high degree of uncertainty (contract work; currently single, but looking to mingle), I'd think long and hard about an alternative to buying in Calgary.
Regarding the 4-plex idea - WTH? In the OP, you talk about wanting space for trucks and trailers, and acknowledge the idea that being a landlord in Calgary these days is "shit" and now you want to combine the worst of both those worlds - a smaller home, likely with little to no spare parking, all well becoming a landlord x3?
As far as the recession not having an effect on Calgary RE - most of the Calgary market, at best, has been flat for the last decade; the high end market is probably down 20-30% (even more at the highest end). That's just gross housing prices, not including property taxes & RE fees. And fuck, nevermind opportunity costs, which cannot be discounted seeing as we're on the tail end of the biggest bull run in history. Nearly every comparable market through Canada (and jeez, most of the developed world) has seen unprecedented price appreciation in their RE and Calgary's... been flat. Hey, I guess it could be worse.
Anyways, I really don't mean to piss on your parade. I would genuinely feel bad for anyone going into a ~$600k RE purchase today without their eyes being wide fucking open, only to have to sell in a couple years and have it cost them something crazy like $100 grand. GL with whatever you decide.