I have read the entire post & replies, indeed interesting and fruitful discussion.
I have to say my opinion is very like @Cody L.
The most important advantage you have when you invest in real estate is the leverage (and I am investing also in different segments such as stock market for example).
You almost don't have any other investment segments in which you can leverage yourself, and use this "additional money" to increase your portfolio and income.
And here is a thing I learned from one of the greatest investors I once meet -
The idea in real estate investment is not to invest your 100% cash. It can't get you far and fast enough.
You should put the minimum cash required and start leverage yourself, and use your remaining cash to do more investments. And indeed - All of the big real estate investors giants use other people money they raise in the market to do their investments.
If you choose correctly your investments and put the money on the right opportunities you shouldn't be afraid to leverage yourself.
And I think BRRRR is like running a marathon - Indeed in the short term you immediate cash flow is getting lower, but in the longer term you can increase your equity dramatically.
The question you should ask yourself how far you want to go.
Eran