Set the second thermostat to whatever you consider the minimum temp to be - I would use 55º - and electrically parallel the existing and the hidden thermostat.

Although certain defenses do exist including, insofar as is relevant here, unreasonable hardship, " 'the court's discretion to grant or deny specific performance of a contract for the sale of realty is not unlimited; unless the court finds that granting a decree of specific performance would be a drastic or harsh remedy, or work injustice, the court must direct specific performance' " (id., quoting 91 NY Jur 2d, Real Property Sales and Exchanges § 204).

But the stigma behind crime still exists, like any city, so it's important to screen tenants.

Keep in mind rent control is 1 thing, its a laws for existing tenants but some city's like Newark are so strict that you must get approval for what rent can be even after a tenant moves out and new ones move in. 

I managed STR with my sister twenty years ago before Airbnb existed.

It may create a problem for you later if your bank discovers the account is owned by an LLC that no longer exists.

Interestingly I saw they’re still in existence with a stock price of $3,105 per share.  

Are you aware of city of San Diego rules regarding converting existing legal space to ADUs?  

Look up ideal existing performing properties, your "hero's" as it were, find out who own's it, and reach out to them. 

However, before deciding on a DSCR loan, it’s important to analyze your existing first mortgages—including their rates and the current loan-to-value (LTV).