I have a spreadsheet of the rough timeline for when roofs and cap ex items will need to be done.

After the must-pay items are handled, then I will apply remaining funds towards rent, late fees, etc.

You should be calculating Cap Ex for all long term items that will need replacement at some point - appliances, roofs, ac, water heater, etc.

The other is end of service life items such as the roof that would have to be capitalized aka Depreciated rather than written off as an expense immediately.

I had to build fences along my driveway accessing a drive under garage, because the retaining wall was more than 30" tall (standard building code item) but these properties were built in the 40s/50s and never had a fence there until I rented Section 8 and they required it.From a tenant perspective, I never had any of the issues James notes.

This got me thinking there are probably other items we need to upgrade in a mountain STR.So here's my question for those with experience in the area: What other items or upgrades do I need in a mountain home STR that are not obvious to a newbie/city dweller?

There were other items on the agenda that were disregarded, which I found maddening.You should also check out www.taxsaleacademy.com if you're looking for training to get started. 

The former developer already had them set, but never developed.Several utility items to do are Water and Sewer along the front road. 

Are there any large capex items you are expecting? 

If builder pushes you saying "come on, don't hold up the closing for these minor items, let's close the house and take care of the them with warranties."