This strategy is really difficult. It is incredible helpful once you get the hang of it and the appropriate expectations. We have 64 rentals, and by and large they have all been via this strategy...but it definitely isn't as easy as I feel a lot of the BP literature makes it seem to be.
All of our deals, we have either started with our money or the money of friends and family...which is private money at 8-12% and no points. We get several SFH - 4 unit properties, and then refinance as a package with a commercial lender.
We lay out a decent amount of capital on the front in...to later be reimbursed as close to 100% as we can possibly get. Sometimes we fall a little short, sometimes we fall very short, and throughout the entire process...our books look like we are 1-2 missteps away from going belly up.
This process pays off extraordinarily in the long run...but a lot of the negative or difficult aspects of it often get glossed over or ignored.