I plan on converting the barn into another sleeping space and indoor/outdoor rec room.

Newsom's plan is lazy governing.   

Congratulations to you for setting yourself a goal and having a plan in place to execute it. 

I currently have a bank account dedicated to my first property which I hold in an LLC, and I'm planning on paying out of pocket for the start-up costs initially but I wasn't sure if creating new savings accounts under my first LLC's Bank constitutes a comingling.

Not that that is a bad thing as some are on lower comp plans but they are at the mercy of all having "overlays" and have to sell their loans.

The data plans are reasonable ($50/month) and the service seems like it would be more reliable through storms and outages. 

However, if you have a more extensive portfolio or plan to become larger in the next year or two, I would look for a double-entry system that allows bank reconciliations.

Are you planning to rent the entire unit at the 2nd year mark? 

If you sell, consider a 1031 exchange to defer taxes if you plan to reinvest in real estate.

Credit, jobs, income, age, married, plans for future all this matters.