Keep in mind this will be at a much higher rate than your current 3.2% interest rate, so I'm not sure if paying off the existing loan is a great choice.

The worst part is that it's usually way too easy to get your license, and the consequences for these sleazy agents are usually non-existent or not harsh enough. 

You're increasing the need for hot and cold air dramatically and it's doubtful the existing system will be adequate.But, in answer to your original question - yes you will need a permit.

The existence of a contract -- I agree with you on this -- may be a complete defense to such a claim. 

I have a note in the lease that they're not supplied or warranted by the landlord and the extent of what I will do (if any exist at all) is haul them away. 

But I do have an issue with asking some of these pre-existing cabin owners to have to retrofit their cabin with the system and expecting them to have it done in a year or something. 

STR would be another option, but a lot of markets are saturated, so you must do your research.

What I typically see investors do to get rolling is use a Heloc or cashout refi on an existing property to get the startup capital they need.

Whereas the majority of the existing clients have stayed with you, but the whale client is with the ex-partner leads me to believe that if this heads to any type of judicial setting that no damages would be awarded.

A lot of times it is best if the existing pm is the listing agent so they can negate this along with tenant communications.