I am looking for some opinions on the best way to quickly scale up a portfolio of buy and holds & Fix and Flips given the below situation.Investor income (day job) - 300k plus annually 
Debt to income - excellent 
Liquid cash on hand - 50k 
Credit - Excellent 
Currently has 2 rentals- (could refi out 60k cash)Given the above stats, what would the community recommend is the most efficient way for an investor in this situation that wants to scale to 20+ properties in the next 5 years?

Can you NOT see how much more efficient that is?   

I prefer 1 versus 4 or 5 deals and consider it to be more efficient and less brain damage, but to each his own.If the place needs kitchen, baths, pools, mechanical work, closing costs, holding costs, I could not get it all done $32/sqft but I may not have the same resources as you.Good luck...looks like a wild project.  

Which is most effective, and which is most cost-efficient?

Fast and efficient. 

I can share your concern, even if I haven't seen your question or their response.The reality is that institutional money is just a lot more efficient and can lend for longer duration than retail money.  

Please let me know if I am missing any steps as to make this process more efficient.  

Should I stay away from this type of property due to it being just efficiencies.  

There are a ton of  'micro-markets' that will let investors specialize in a particular area and be very efficient in them.

His feedback seems incredibly important to maximize efficiency, especially if you work full time.I still have a huge checklist to make this all happen, but I'm trying to take small steps every day:1.