In addition, unit 2 has some basement space converted into an additional bedroom and bathroom and also an additional kitchen. 

Maybe they need additional time in the house?

*always make sure that its in writing that ALL change orders or additional work will be in writing before its started.

Additionally we have cleaned the property and documented all.

We have clients using private banking systems to gain additional revenue on their rental property.

There are coastal commission guidelines in addition to the zoning and building department requirements.

If I were you, I would look into the HELOC to access your additional equity.

Additionally, the schools for this neighborhood are excellent.

I do however, think that it would present a very unique opportunity for a buyer with children whom wants to relocate from the city (easy commute in) and perhaps have additional rental income, OR move the in-laws into the ADU. 

In addition, try to network with a realtor who may have some buyers that had deals fall apart.