We can easily cover the mortgage with our W2 income and we anticipate we will cover the mortgage and then some with the STR income (it has a track record of this with current owners and also comparing data from surrounding comps).

What I wonder is how the LLC gets enough of a track record to start qualifying for loans? 

So far we are relying on Google Sheets to track everything but it's very manual.

It's easy to keep track of a handful of rentais, so I would handle it myself but it wouldn't hurt to talk to a tax pro if you're unsure. 

You can see how it tracks relative to apartment rents, its understated in the inflation numbers reported.

Generally our process as property managers is to start right on track with market rate and assess activity on a weekly basis and recommend changes that may help activity such as price reduction, changes to allow pets, include utilities into the rent, move in specials etc.

Crowdfunding makes real estate easily accessible, however, in regard to institutional real estate investments, the advice of an expert who works in the industry every day, knows all the players and their track records, and performs due diligence on each offering is a great benefit to you and comes to you at no cost. 

It seems that you are on the right track though.

I wonder how more experienced STR operators keep track of these supplies?

Lines of credit are available to operating companies with long track records of income.