This is one of the best questions that I have seen asked on this forum. I personally feel that many investors are going about this in the wrong fashion.
I make over 100K per year in cashflow. That is set to go up in the next few months. A refinance, another storefront lease, and perhaps one more purchase, the flow could be up around 170K. That does not include one of the deals that is still in rehab mode and is not cashflowing yet.
There are so many concerned with a house here, a house there, perhaps a fourplex thrown in. This will get you cashflow over time but there are faster ways to approach this.
BUILD CAPITAL FIRST!!!
It does not matter how you do this, just make money the best way that you know how. If that means working hard on your high paying job, flipping houses, whatever. I personally use value add apartment deals to make chunks of money.
Once you have enough to matter, say $250K, then you can leverage into something worth 1M. Buy a strip center or other commercial building. Or, buy an apartment building that has cashflow. Better yet, buy some undervalued asset and make it cashflow even more!