For almost forty years, mostly in Alberta (Canada), I have done most of my own construction, renovations, home repairs and other mechanical/cable/stereo jobs myself. For mainly two reasons: (1) Whenever I had hired someone to do work for me, it was not done right. [As we always say: If you can’t do a job right, don’t do it at all!].  (2) In the long run, I saved myself a lot of money. Over and above I also learned a lot, about carpentry, framing, roofing, flooring, dry walling, painting, electrical and plumbing to a certain acceptable degree. If possible, never using a ‘handyman”.
Alberta jobs – because of residing outside the city – mostly involved ‘city and country’ type of construction, which is different from city type of projects. Including miles of fencing and clearing land. Septic tank, underground septic pipes, well and pumps, large (electrical) transformer work (all electrical done by a friend Electrician).
Nightmarish examples, found after moving into a new home that needed changes: Bathroom plumbing reversed (that is hot and cold taps). Building a new kitchen in a fairly new house: Bowed 2×4’s sticking out of the walls. Needed removal, drywall repaired before tiling. One example where I had hired a small crew (managed by the sellers of the barn package) to put up a horse barn. The blue prints were reversed, using inside wall measurements for the outside, inside no room for the horse stalls. Needed to change the entire barn design. Over and above, large 4 inch nails sticking out into the stall – not so healthy for a horse. Typically those types of people I had to throw off my property.
One might think that a large job in the country comes with large problems, not so. The worst, yet, had been a condo in an older building, in a city. Biggest nightmare ever. Big holes cut into drywall to attach light fixtures to the raw main wires. Plumbing totally shot, electrical likewise. Chewed up pencils used as shims in the closet doors. To just start renovating and improving, I needed many months of repairs. Doors cut too short when ordered, did not fit. Needed to rebuild closets instead to make doors fit. On and on.
It is common knowledge in many parts of North America that construction costs are extreme, because of certain practices whereby money is skimmed off by those who supply the workers, but in fact do nothing themselves. Overhead, it is called. We, as customers paying for unnecessary overhead. Workers ? Although unionized, but not paid enough by those who shovel your hard-earned money into their pockets. In the old days, everything was nailed, a nightmare in itself. [According to: “Give a man a hammer and he treats everything like a nail.”]. The worst, yet, are those armies of ‘handymen’ (retired old guys) who take unsuspecting senior citizens ‘out for lunch’ (ripoff). They waltz into your home, do some work, often do not have their own tools, and always want to get paid in CASH. It is a criminal offence to practice tax avoidance. Write that behind your ears, Mr. Contractor !

Over and above, the worst is those kind who come on to you, want to touch you (they call it hug you) with their filthy hands. As the last one did. Who should have a tattoo on each of his lower (butt) cheeks : a Swastika, and the Hammer & Sickle.