I do believe there is merit in following simple best practices that have asset protection as a side benefit:  1) Taking out large mortgages on properties to minimize equity; 2) Having adequate liability insurance; 3) Contributing assets to retirement plans and other protected vehicles; 4) Dividing ownership of family assets between yourself, your spouse, and your children; and, especially, 5) Running an honest business and treating people fairly.  

It's true but it's not that simple. 

Thank you @Scott TrenchI was looking for something simple, where the tool can help me with building the real estate portfolio.

This gets complicated and is not a DIY project.And, depending on the specifics, various other limitations can come into play.

When you need 100+ of these or even a few hundreds, it could take hours and hours to DIY.

You can DIY, but based on all the things you have said, I think it is time you hire an attorney. 

If it was about buying properties, it would be called "collecting".Assuming a property that is good for both, one simple way (the best way) to see which is best is based on comparing the potential profit from a flip to how many years it would take for the potential cumulative CF to equal that potential profit. 

If you are behind and this would be your last property to ever buy, I actually would consider getting the fourplex and then put the net profits into another investment (simple as high interest savings or even into the market).

I wouldn't worry about getting a real estate focused accountant just for this simple test.

There is free software online too, like Wave which gets a nod from a lot of folks with simple businessesI recommend hiring a bookkeeper if you are going to scale.