@Alexander FeliceSFR, especially if it is your primary residence are difficult decisions, and thus what I call emotional decisions.

Not the say the tenants don't use them as man caves and hangout spots.I am house hacking too, but on a more permanent basis.

I just don't want someone coming after my personal residence if the bottom falls out of the market.

Suggest you find someone who can set up a trust for probate etc and they can recommend which state for where your LLC should reside.

Is this a flip, a buy/hold, or intended to be your residence?

Should we cash out refinance out primary residence to pull more cash out or should we just use own cash reserve+ HELOC for next down payment and any extra fees?

My question is the following, if I buy an investment property (while continuing to rent where I live), does that prevent me from qualifying for an FHA loan later on when looking to own my primary residence?

Even when house hunting for my residence a house would be gone within days of being listed. 

(we also have a relocation package that we need to use up in 6 months)So if my goal is to move out of that duplex in two years after finding another permanent home, will I have trouble getting another substantial loan (I am on a W2)?

I'm talking about for my personal residence by the way, just in case I didn't make that clear.