That said, the GC I am looking to use has told me it would cost me more to build a duplex vs two sfh's (same sqft) r/t firewalls etc when it comes to additional steps for adjoined units.

Does the garage have proper firewall protection and heat alarms for whoever is sleeping there?

These are townhouses built side by side, sharing a firewall in-between.

Fire suppression, fire walls needed, Sewer/Water/bathrooms/electical breakout, etc  Determine cost effectiveness.  

I have been told that mice can still come from the other homes connected to mine, via bitting through the firewall, and make entry again. 

Most of the really good data is behind paid firewalls.

Perhaps we (BP, the community) need a better firewall between the visible personalities - podcast hosts, webinar leaders, etc - and those with something to sell.

AND, I would require that there be a smoke detector in the garage that is "connected" or "talks to" the smoke detectors in the house so that if a fire does break out in the garage, the tenants can get out out before the house burns down.I would also make sure that there is a sufficient fire wall between the garage and the rest of the house.

Together we can "fire" Wall Street and the leaches sucking us dry, telling us there "too big to fail" and how we must support there elitist existence so we can be allowed our pittance in return.   

My biggest surprise on this last project was that they allowed standard 1/2" sheetrock for fire wall.