Either that or you take it to work.

Having permits covers you for house insurance if your house burns down they won't pay for your basement
If it's a Reno and already has a basement before no need for permits
I am a plumber in Calgary

I suppose that only works for those who work in construction....

I suppose my only advice would be (probably obviously) to make everything that might go wrong - accessible. Drop ceilings / wall panels etc. FI it's likely the plumbing donstairs is directly below the plumbing upstairs - so if you have a blocked or leaky toilet / flood of some kind upstairs then it's going to come through the ceiling.

This happened to us and thankfully we had put in the drop ceiling (much to my dismay as I hate it) but we only had to replace a couple of panels.

Not necessarily. There is a big open dumpster round behind the office Mrs P works in.

Looks like a power-to-light with a 3 way switch, a lot of basements start off like that because it's way cheaper for the building contractor to run the power round the lights and then onto upstairs. Perfectly legal as long as the number of conductors doesn't exceed the max for an octagonal junction box of that depth. (Messy, i know.)