I would say high-quality bedding, cozy outdoor spaces with firepits or seating, and thoughtful touches like local coffee bar setups.

That is a great place to start, as well as hitting some local real estate investor meetups so you can meet some other house hackers in person who have done what you want to do.

For example, properties became available at the onset of COVID, during a snowstorm, a hurricane, a major holiday, or after some other unexpected event.

We took the reverse action and started lowering asking rents until they moved.I suspect the reason that one property of yours turned quickly is because your asking rent was very favorable vs. local competition. 

Only five of the qualifying 25 local cities saw a population decrease, topped by Bee Cave (-2.7%).

Investing locally in the Bay Area will come with higher acquisition costs, but appreciation can still build wealth long term, so don't be weary if you're property doesn't cash flow right now the bat.

But again, dedicated crews drive reno costs down.If you can connect with a flipper in your area (quick out your local REIG) and ask to come along when they scope out a job, you will get more from one or two trips than from a dozen books. 

I would do what you are doing here on a bigger scale - social media, local markets she operates in Facebook groups, etc. 

You will also need to check your local laws for any strict laws that may make running an Airbnb hard.

The best way to find an investor friendly broker is at a RE meetup, but you can also just ask around in your local network or google.