So are you trying to avoid pulling permits? 

Understand the local permitting requirements, keep eyes on your property to avoid squatters, and make sure you have a great vacant insurance policy while you're renovating.

As someone who has served on a permitting board, I can tell you that a good relationship goes a long ways.

For our ADU (garage conversion), I am handling the design/engineering and then selecting a final contractor once its permitted and ready to go. 

Great hosts will be good neighbors, will contribute to local tourism and will pay their taxes and permit fees* A major area to improve on the proposal is the 1 hour time-limit for resolving complaints.

As an example, we decided to replace the windows in a house we were renovating and ended up costing us $50,000 extra because we got into issues with permitting and suddenly found ourselves having to hire an architect, speciality contractors, etc.  

Sometimes, buying an existing property can be more cost-effective and less time-consuming and maybe require slightly less permits, etc. 

Just make sure you have all the required permits, including alcohol.

We then reach out to those contractors and onboard them like any other contractor - so we ensure insurance is up to date, workers comp in place, licensed etc.  

It sounds like you have an un-permitted unit, which is essentially always a risk since there has been no notice to the AHJ that it exists and they can therefore initiate a code case to have it removed in most cases.