CPA pointed out that while it adds complexity to banking and bookkeeping, running the LLCs as separate businesses and separate banking bolsters their position as LLC's in the event of actual Liability issues that would be better contained in on LLC.

The idea here was to maintain our cash situation (we have two kids, maybe another on the way soon, and a 170 year old house) and yet enter the rental market in good position.

I see that as a positive having the US Postal service in your building, people still go to them and you will have a steady income.

What I have going for me - a Class A Contractor’s license, a healthy W2 salary (I’m an engineer at a “think tank”), a little bit of experience, and about $25k or so in the bank for my next investment.  

Are you in first position or second? 

In addition, I expect to have a positive cash flow on this property for $350 per month, giving me a good cash-on-cash return as well on that $20K.

from my point of view if your an individual and not partnering with folks who ever is going to sue you is going to name you personally.. this is where you need good insurance to take up your defense as your first line of defense.whether they have the right to sue you is immaterial.. or whether they will prevail is immaterial.. if your operating as a group or partnership and have clean records this can limit your exposure to your ownership.other than that  retirement accounts should be maxed out they basically cant be touched... certain trusts.but just LLC labyrinths like you mention.. those are not going to do it for most or.. you will spend a ton of dough fighting to make the position they can't sue you. when suits happen everyone is named .. that's when you need good insurance to handle your defense.

Currently I am aggressively establishing acquisition position to begin developing buy-and-hold portfolio consisting of residential multifamily (3-4 unit) and commercial multifamily (5-20 unit). 

I'm actually a big fan, and as mentioned above, have mostly very positive experiences.

I had looked into it in the past and there was a time period that needed to pass as well as an equity position beyond 20% that the mortgage company wanted me to have reached (I believe it was 25%) for PMI to drop.