My initial plan had been to do something like Rent-to-Retirement or REI Nation- assuming that I'd be leaving money on the table to pay for their expertise, but hoping that I would learn through the process and develop the confidence to strike out on my own later. 

Anyone can do it just like anyone can flip a house or run a short-term rental.

We are considering stepping in and trying to buy the place, but looking for some guidance on STR and what kind of money this place can bring in. 

Something I should be adding into my calculator when I run numbers?

Very short seasoning period.

It's simply a better way to run your checking and makes your money work for you constantly instead of sitting around waiting for you to do something with it. 

I’ve been a real estate investor since 2015, owning and managing multiple multifamily properties and running a short-term rental business in Cape Cod, the Lakes Region of NH, and the Berkshires.

Well, he spent all the money in the account, a lot of personal expenses and paid himself money.

Quote from @Pearse Cafiero: You want to borrow money to buy a house, but you don't have the downpayment.

Does the seller owe the buyer money or does the buyer owe the seller for property tax prorations?