I'm going to go out on a limb here. Please, before anyone tells me off, I am not at all trying to pull down Quyen's achievement, because it certainly is an achievement, but I am merely trying to put it in perspective.
There are countless stories of investors that have a similar headline (if we were to write about them all), of either from $0 to $xxx in x years, or from 0 to x properties in x years. Realistically, anyone on a large income and a (close to) paid off PPOR could borrow and purchase a huge amount of properties in a small timeframe. Admittedly most don't, so this immediately puts Quyen in a completely different category to the rest.
The headline is meant to turn heads, and turn heads it does. It sounds like the person went from being penniless to a multimillionaire in a few short years, when the truth is far from the fact.
Given the yield on those properties, Quyen may have difficulty in accessing more funds to further his portfolio unless he gets a bit creative. I don't know if he has fixed his rates, but if not could be vulnerable to interest rate risk given the fact that there seems to be a large amount of neg gearing in the portfolio. Of course, I don't know what income he is on, his starting savings or the value of his PPOR so there could be some wriggle room, maybe even a LOC sitting idle for such emergencies.
More impressive to me is the nuts and bolts of the story of the person on a small income who has built up a portfolio properties and can then retire on this income. Brenda comes to mind. A stay at home mum (if I remember rightly) and a school teacher. One average income and built an empire that the family could retire on. To me, that is impressive!