As a longtime rental manager I learned long since not to do any of those things. I want the plumber/electrician/consultant to do ONLY what is in his or her line of expertise. I prepare the site and I clean up after him.

And then I let them do their thing. I stay with them- there are very few times that I don't learn something valuable.

The only stereotype I have found holds true is that plumbers are in the one trade that you have to watch like a hawk - they'll use a short axe to open a wall to reach plumbing. I suppose that there are individual plumbers that don't do that- but I suspect most of them consider themselves in the order of fire fighters.