I just used my attorney as our registered agent, PO Box as our business address, and a separate LLC as the holding company. $50/ LLC and it literally takes less than 20 minutes for each LLC and costs less than $20/ yr. to renew each LLC.

I took the Airbnb bookings and now I'm around 80/20 Airbnb/VRBO.Based on a recent bad experience that I had with Airbnb (it's a separate thread out here), I called VRBO and asked them how I can get more booking requests from VRBO. 

I would suggest doing these separately however since you will run into issues with a partial release clause on a blanket loan.

I'd have to see your overall layouts but I think you are on the right track. we build 3 story stacked triplexes and it's very efficient so don't be afraid to go up either. anytime you build more than 1 structure costs are much higher but if its just to offset mortgage and you want to be separate then I understand. 

At its most simple we’re separating the appreciation/capital buildup benefit from the cash flow benefit.  

I am now under the suspicion that their friend, the one who is still living at the property, is the one who created separate accounts for all three of them and did the signing for each individual who is under this lease agreement. 

I think if you are going to keep all three parties involved as owners of the deal long term then you need to separate yourself as a renter and a contractor.

Savings: Hold the deposit here so it's separate from operating funds.

You have to separate the two.

Another idea could be to see if the HVAC system can be adjusted or modified to better separate the airflow between the units.