I don' think anyone is suggesting that simply managing these 9 properties is enough.

They simply skip over/ignore concepts like vulnerable persons, equity skimming, equity stripping, bank fraud, wire fraud, mortgage fraud, escrow and closing, etc  It's now the "thing" to do.What could go wrong?

So some things will be easier and more convenient (one roof to repair) but many tasks will simply be a multiple based on the number of doors.

What I'm seeing in the industry as a cautionary tale for you is that simply the reputation of the company is not going to necessarily carry the day.  

To prove payments you could simply show your latest statement to the lender denying you hundreds of thousands of dollars.

I would start by finding areas you actually WANT to live and go from there.Picking a place to call home simply because it has a real estate market that you feel will fit your goals is a great way to end up miserable. 

It would simply be another level up from the LLC taking title.

Others have simply created a new listing and had the seller notify guests about the change.

With broad, high-level criteria, you may be able to easily cross of a number of neighborhoods where the numbers simply do not make sense (assuming you already have your buy box nailed down).

You simply get a discount on this purchase, equal to your tax rate.