If the latter, would that create unnecessary tax implications?

Of course, you could always do it by stealth and just take your chances, but if some unnecessary misery were to befall any of those sellers/homes and someone could trace any of it back to you (i.e. the criminal saying "Well, I knew what was in there because I saw this video"), then you could also perhaps be successfully sued. 

My thoughts are the pool adds unnecessary liability for not much more added monthly revenue.

You've just created an increase level of complexity that is completely unnecessary.

This cuts down on a lot of unnecessary driving and wasted time. 

Investment LLC" is the umbrella company, but "Investment LLC-1," "Investment LLC-2," etc are the series LLCs under it that own the individual properties.It may seem tedious and unnecessary to create all of these series LLCs, but you need to protect your investments correctly.

There are different schools of thought that you should proactively replace windows which can be pricey and the house might have passed any way, you can proactively paint with someone who is not a lead contractor which would save money on the painting but still may fail or could have been unnecessary, or you can test and roll the dice and deal with the consequences if you have lead. 

Seems like an invasive and unnecessary process.

Those clients were certainly paying thousands of unnecessary taxes just from a lack of systems to track deductible expenses. 

---Profitable: the expense generates more revenue for your business than what it cost---Necessary: the expense is necessary for your business to run but doesn't directly generate more revenue than what it cost---Unnecessary: the expense does not generate more revenue for your business than what it cost and isn't necessary to run your businessWhatever turns up unnecessary, get rid of that expense as quickly as possible!