@Joshua Viksman I usually answer the calls and let them talk for as long as possible, hoping to just waste their time while I continue doing whatever I was doing.

In commercial almost anything can be possible you just have to ask and see if they say YES as long as it's legal.  

One specific thing I put into all of my contracts was that I could get out of the lease at anytime as long as I found a new tenant to replace me OR paid 2 months rent.

The two PM companies are using Appfolio software and I have heard the bookkeeping features are pretty good, as long as they are good at inputing and using the tools.

This would imply the tenants could keep the garage as long as they desire (or until you can terminate occupancy through one of the legal options)  Assuming that your duplex is exempt from the state wide rent control, the tenants have the right to the garage through the end of their lease (May 2022).  2 months prior to the lease being up, provide notice that the garage will not be included at the end of the current lease.  

@Ryan Schrope An in between phase and good as long as you can save a little money a long the way.

As long as you don't bring in other lien holders, I think it should be fine. 

------as long as I don't go over that 75% loan to home value threshold I may be way off, if so please educate me. 

I don't see how it's the tenants business as long as they're all dead.

well as long as you dont have affordability issues in the future like the Bay Area  this will be a nice win for the area.