So when the opportunity came to us to buy US properties, we took it, and are growing it in a way that will secure our ability to pursue more deals in the future, while opening up better markets - This is hard to do as a singular Canadian Investor, which is why we chose to help others, because they can help us achieve this goal. 

I'm sure there's not one singular place to find four plexes, but do you know of any other places I'd be likely to find four plexes?

You could theoretically do it with one property if you have a short-term rental, materially participate (don't need to rise to being a real estate professional for this) and accelerate your depreciation for a singular year.

@Michael Conklin Arizona had the 3rd fastest growing GDP in Q4 2019 according to Phoenix business journal behind Utah and Washington.www.bizjournals.com/phoenix/news/2020/04/07/arizonas-2019-gdp-growth-among-top-in-the-nation.amp.htmlI’d argue that the relative GDP trend of a singular city is much more important than the its GDP compared to other cities.

Micro is NOT used to define economics of a singular business, thats called accounting buddy. 

With an SDIRA its a bit more singular in use.

Basically, become singularly focused on that first piece of property.