Be an area expert on contracts, zoning, value add components, contractors, and so much more. 

In the northeast having a second heat source in the rental saved  frozen pipes when the electric was out for days.

I’m a contractor with a couple single family homes for rent.

Contact a couple contractors to see what the cost would be to add the addition.

Since you plan to travel often, focusing on systems and building a reliable team: agent, lender, property manager, and contractor. 

Had a home inspection done and found it needs some work (Roof will need to be replaced in the next few years, some of the electrical needs work, updating the 2 upstairs units, furnace replacement at some point, etc...).  

My name is Rebecca and my husband, Nick Knox III and I have run Captain Save a Home LLC, Brew City REI Club, Brew City REI Training Cafe and Wisconsin Contractor and Handyman Club based out of Milwaukee, WI for over a decade.

Virtually everyone has used an electric range or oven in their life but lots of people have no experience at all with gas anything. 

Also consider contacting houses that look vacant, simply door knocking in a neighborhood that you are interested in and talking to the homeowners in a genuine way, For Sale By Owners is another potential, using an App like Nextdoor or Facebook pages/groups related to local real estate and just telling the group what you are looking for, contractors also know about houses coming on the market soon and so do property management companies, and finally garage sales are a good way to find off-market properties as people prepare to sell.To Your Success!

You're a contractor in the Bay Area, I'm guessing you're slammed with work.