Psychology and sociology is paramount in this aspect. 3- The business of the business: This is things such as regulatory actions, licensures, the constant changing of such, how to navigate, contracts, documentations, process's and systems, etc etc.. 

@David Cianci, from a marketing side: think about thought leadership campaigns, but also knowing how to define a customer base, develop messaging that resonates with this customer's pain points, and offering a clear solution for them.  

Further extrapolated, "pain = profits".

Yes having a mentor should prevent some growing pains, but those are the best teachers.

They pain up front, overnighted monies.

I feel your pain.

“Why questions” allow you to find out about issues you did not know existed, pain points that you can solve, and “black swan” desires that can net you amazing deals.

Giving up a lower rate on the full financed amount with a refi would be much more painful than just having a second mortgage at a higher rate that was big enough to pay off the CC debt.  

Anything short of separate metering is going to cause pain.

I am a mid level real estate investor with scaling pains and would like to know what Mastermind groups are out there for investors with 20+ units that are looking to grow to 500+ units.