(Strikingly similair scenario to someone in another state telling someone what the regulations are that govern the profession they practice full-time in that state are, no?) 

Why is this practice so prevalent?

@Bill GulleyI wasn't anticipating, nor even expecting, you to advise on how this might play in Canada (that's why I tapped @Claude Boiron), but was hoping you might add some depth an clarity to Frank Chin's initial reply above (as typically practiced in the U.S.A.).It's intriguing, but the more I have dug into the idea, I'm still not convinced it's something I could pitch to a property owner easily.  

And with houses only 1000-1200 sf, they practically build themselves. 

David Zheng I think it comes down to if you have a "practice" or a "business".

Underpaying people is a bad business practice.

Also, there are a few best practices that are good to know as you begin your journey. 

So people come in from all over the country to train here, and get loosed on our market to practice their testing.

Much more practical for draining dishwasher.

@Art Maydan, I love the theory of separating the water, but in practice, it sucks.