For example, a hot water heater is ready to go versus a bathroom you want to upgrade.

You need 2 hvac systems , 2 electric meters , you should split the units and submeter the water .   

Certainly replacing a furnace and/or a water heater would require a permit as well as running a new or replacing a duct run.

Private, heated pool.  

In our opinion, many OOS investors set themselves up for failure because they don't truly take the time to understand:1) The Class of the NEIGHBORHOOD they are buying in - which is relative to the overall area.2) The Class of the PROPERTY they are buying - which is relative to the overall area.3) The Class of the TENANT POOL the Neighborhood & Property will attract - which is relative to the overall area.4) The Class of the CONTRACTORS that will work on their Property, given the Neighborhood location - which is relative to the overall area.5) The Class of the PROPERTY MANAGEMENT COMPANIES (PMC) that will manage their Property, given the Neighborhood location and the Tenants it will attract - which is relative to the overall area.6) That a Class X NEIGHBORHOOD will have mostly Class X PROPERTIES, which will only attract Class X TENANTS, CONTRACTORS AND PMCs and deliver Class X RESULTS.7) That OOS property Class rankings are often different than the Class ranking of the local market they live.8) Class A is relatively easy to manage, can even be DIY remote managed from another state.

We are leaning towards testing the waters for putting it on the market even though originally it was going to be a long term buy and hold.

Water, air, sewage?

You may be dead in the water. 

I'm in Cuxhaven Germany and reaching out to German and European Bigger Pockets members because I'd like to set up a European Bigger Pockets Master Mind group.One of the purposes of the mastermind is to focus on pooling together resources, be it funding, knowledge or expertise, for all the deals this growing group might offer.

Without knowing more about the location though, if this cabin has direct water views and is able to sleep at least 6 people, a fully renovated version of your cabin could probably pull in at least $600/night in the summer without much effort.