These are just a few items that may not necessarily jump out to you in your excel spreadsheet but are often realities of owning a condo. 

If you brought your spouse and 2 kids with you, and you could argue all of your argue of your time on the trip was looking at real estate, and your personal business and activity circumstance defends being able to immediately deduct it and not treat it as a start up cost... likely 75% of much of the travel costs (airfare, food, etc) would be non-deductible. 

Hopefully, your lease says the tenants cannot modify the property without your permission.Some of the other items could be ordinary maintenance requests or something you are just stuck with.

It is "possible" to apply classes to almost all of these items but since we have chart of accounts for different buildings even within an entity our chart would look crazy. 

Just my food for thought here

The new boiler, all associated work, and extra items were around 7500 including permits and inspection.

Might be a little lower than a purchase, but you will still be paying lender fees, title fees, escrow fees and prepaid items. 

Also, leaks cause damage to the drywall and other items.

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?

Sometimes the HOA can cover capital expenses like roof and exterior, so that can help cash flow as well, but the HOA might increase the dues when they have to pay for capital items.