There are also winter issues (e.g frozen pipes possibly bursting and having to crank up the heat to prevent that) that we don't deal with in CA.

Unnecessary costs for a cash-out or HELOC doesn't make sense unless you plan to live in the house for a few years.  

The duplex I just got I am putting in 10k just for preventive maintenance making my all-in price 90k, with 20k in rent.

There is a delicate balance somewhere between keeping legislation strong enough to protect homeowners, while also not burdening the industry so much that people choose to do work illegally as you suggested, or take unnecessary time to deliver a finished project (and thus a home for somebody in this case).

The single-minded focus on cash flow, even while house-hacking, has prevented so many people from buying here in Denver and Colorado Springs. 

Trust, you will crowd out alllll sorts of unnecessary stuff if you do that one thing.

I don't know if there are privacy protection laws preventing this in Canada though.

Our first contractor screwed up the flooring, he did not handle the sound prevention so now the neighbor underneath is complaining the noise from our floor.

My realtor informed me that he attempted to persuade the buyer to increase their offer to $224k, but their budget constraints prevented this.

What else would you screen to prevent this from happening?