Start with BiggerPockets Ultimate Beginners Guide (free).

.- Someone talked about crime and hard tenants (who don't pay - usually inherited ones)- not many economic opportunities to attract pool of people and boost area etcI'm looking at houses on both sides (Canada and USA) US, they are cheaper like 731 Pine Ave, Niagara FAlls NY 14301 going for $270,000 (5/2, 2700sq ft) but on Can side, it's like houses are in the US$400K - smaller sq ft.

It's just unfortunate you were not notified to get the plumbers out sooner or the PM did not communicate not to leave the faucets off but ultimately if they were left off you likely would have had pressure built up and pipes burst (especially if they lines weren't all PEX) so the root issue of not having heating water lines still was the issue.

He ultimately refi’d into a loan that felt hefty at first, but it freed him up to add another unit in the building.

Ultimately I'd ask your CPA.

To simplify the scenario I'm envisioning let me put it this way: what does a BRRRR look like when one of the parties contributing to the down payment and rehab costs ultimately ends up being the renter as well?

Ultimately, I do think S8 requires scale and lots of efficiencies but has its benefits. 

Ditto, I use PriceLabs for my STRs - here is a nice writeup ...Airbnb Smart Pricing Vs PriceLabs: An In-Depth Comparison For Hosts | Boost Your Short-Term Rentals

There is the Experian Boost that adds monthly utility bills as credit and various apps and facebook groups.

It also offers a chance to shift into something more passive, reducing the hands-on management that seems to be more of a hassle now that you’ve moved.That said, the rental income potential from your properties is worth noting, but there’s a limit to how much you can boost your cash flow, especially after already making significant upgrades.