I also definitely have an interest in BRRRR for single-family properties, as well.While I have minimal experience in real estate to date (own my own house, plus converted our old house to rental), my father has been involved in the business in Austin, TX for over 10 years now...the apple doesn't fall far from the tree!

It's not "apples to apples".  

Setting future goals without knowing what will come tomorrow is actually designed for people that feel they lack motivation without the apple.

Apple app

Take a look at some of the Open Source software licensing models like the following: Gnu, Apache, Sun, Apple, and BSD.

I would say a property that rents for $500 would need to be purchased around $25K, but as the rent increases, the rent/price ratio can go down.Even after appling the 50% rule (which is NOT the same as the 2% rule), and assuming 30% down payment, a property like this would return $215 a month in true cash flow for a 17% ROI.The duplex for $52K with $1050 in rent is a good deal, too.Equity matters because you need to be able to take a down turn and cover your sales costs.

Make sure you're comparing apples to apples.  

But if other housed are selling for 10K less (apples and apples), then you should be able to find one for 100K or less

You want to compare apples to apples, so if in the subject property each side has 2 bedrooms, 2 baths you want to use comps where the other duplexes each have 2/2 each side.  

I have a door magnet on both sides of my truck advertising my houses.