We are following the BRRR method, so I’ve been doing my homework, but have a couple questions for the experienced. 

However, if anyone has recommendations on alternative methods for securing capital like private lenders, please let me know.Also, I'm in the process of learning how to underwrite through online courses, but finding rental comps for MF seems a bit more complicated than single family homes.

Just to be clear, did M******** ever pay you outside of Zillow or did she mark the rent as "Paid Offline" without you receiving any funds through any method?

The easiest is to become an affiliate and make a referral fee.The mega giant hard money lenders can make money netting 2% by lending hundreds of millions of dollars.

They won’t want to lend you 100%.Your cheapest and easiest plan would be to rent back.

They also offer tenants various payment methods, which can simplify the process for everyone involved.

We totally get the premise behind the Brrr method but at the same time, if you can utilize the same cash principle to buy a bigger, better rental house that will appreciate well over time due to location, wouldn't it also make sense to consider using the cash house equity for this bigger location house to be refinanced later at a lower rate and take the equity out of the better location house then and use the equity later?  

I'm open to other creative methods such as Cash App, Paypal, etc. ... but I believe that they charge for automatic ACH payments.

Closed off spaces were just as @Bruce Woodruff said, a relic of times when you either had servants that worked in industrial spaces and methods that were a lot more crude than today, or when people were poor and could only afford to decorate out a single room as a "proper" place to entertain guests.

They will often recommend what is easiest and most profitable for them over what is best for you.