I had to speak to almost 20 different banks before I found one with less stringent terms that would refi with my situation (type of property/location/etc). 

There should be risk control measures (commonly known as insurance, diversification, etc).

So, in essence, both won't help you retire in your 40s unless you put in major amounts of money, if that major money values high due to market conditions, and if your penalties are not stringent enough to pull from the income you expect to earn accordingly...a.k.a., too many IFs.I wouldn't be concerned with a number value on how much "cash" you should have.

There are 2 measurements of right & wrong on these matters. 

If going the conventional several mortgages route, what are other safety measures to minimize risk besides a good insurance policy? 

What measures are you taking to ensure you get into front of the line Sept 1 for eviction filings?

Rent to own in Texas for a period to exceed 180 while not illegal has requirements so stringent that even the most knowledgeable investor will not do one

On Friday, May 8, the Arkansas Supreme Court announced that "beginning May 18, 2020, Arkansas courts in all divisions shall resume conducting hearings with certain measures to combat the spread of the disease to the public . . . ." 

And many of mine only call when they are not able to fix the issue in the first place.The biggest downside I have had was the annual reinspections continued to get more and more stringent and expensive.

I can measure what your projected 2020 returns will be with your current position and compare what your return on invested equity would be if you did a cash out refinance at X% Loan-to-value with todays rates.