so there are several moving parts we're effectively discussing.

Don't know if it is meaningful or not, but even with a $0 down payment you still are "into" the house for some non-zero amount - you probably have paid closing costs, an inspection, etc.You could always estimate those costs, and use that number as your effective initial investment in the property.

That every time a mortgage is signed and goes into effect, a "note" is created that is able to be bought and sold.

Now their price is taking off because many have been priced out of SFRs. 3) A good HOA can actually be a true benefit to a new owner in that it can more cost effectively manage some basics like lawn care, pool maintenance and other exterior chores where there is economy of scale.4) A bad HOA can cause your property to loose value even in a rising market.

Location selection might be the better back up plan long run.

So this makes effective use of your nights and weekends critical. 

Has anyone out there purchased an investment property in a cost effective city while renting in an expensive city (such as Toronto)?

Once you know your What you could sell them for, then you can answer the question of what is the effective ROI based upon current valuation.

How can you possibly do it that cost effectively? 

You don't know how to wholesale effectively, and you want to virtually wholesale?