Once you start co-mingling the LLC's business with anything else you give an easy and clear reason for anyone suing you to claim the LLC isn't acting like a separate entity and "pierce the corporate veil" meaning that they could use that as a way to come after your personal assets as well.

We keep the main house separate by locking the door between the bedroom and our living area, so guests only have access to their room.

ALWAYS use a separate phone number that rings to your cell phone, like a Google Voice number or some company that offers a phone number.

The methods of separating the owner from their funds grows... and the industry will continue to adapt. 

LLC-A can do a consolidation exchange and purchase a tic% of the new property with all of it's sales.LLC-B can do a simple exchange from it's sale to a tic% of the new property.You can separate by address if you want. 

also keep in mind these are separate business ventures.. and one venture does not bleed into the other..

Another cheaper option would be to just separate the meter and have the two tenants pay for their own electric.

We don't have a PG for any of our DSCRs, and tax wise have it completely separate from personal. 

We currently have a LLC that owns our existing rental property and we run the short term rental activities through this LLC with its own separate bank account.  

The interesting this is, I told the agent that I have gone to properties with a separate garage that required me to pay (just recently in Nashville) and they said that is against their policy.