The biggest mistakes are typically at purchase - over paying or missing large rehab items needed.

Though the previous tenants lived there for a long time and kept it up, it may cause issues if the new tenants ask you to fix items that may not be necessary.

My lender offers credits to offset any of the estimated items that come in higher than expected. 

Are you not able to secure traditional financing?

I would take exception with one item in your description.

You can then compare that to the company you mentioned and pick the best fit for you.The primary item to watch for would be prohibited transactions.

My thought is to put together a database of big ticket items (roof, siding, water heater, appliances, etc) that I will update with prices every year or so. 

I've been debating the merits of STR vs investing in a buy and hold/traditional rental.

So sorry that you have to replace all of those items and deal with it while guests are there..

Just a quick thought, but if it's not something that drives you I wouldn't commit just to have access to it.While Multifamily properties are the typical and traditional way to house hack and build wealth, we have found that in Colorado and the Denver area specifically, they have some pretty big cons.