I'm in a couple of funds so the range is 10-12%.  

One thing to consider is that in terms of wealth building and Kiyosaki's Cashflow Quadrant, owing a rental and doing work yourself is putting you in the self-employed quadrant, not Business Owner or Investor.I think there are a lot of factors stacked against California for long term rentals, and I think you know it too! 

I think another factor here in determining whether its a good investment is your age and your goals. 

(Of course, there is a factor that higher rating will increase my booking but that is not just coming from adding one or two amenities) Besides item 5 and 6, I am not sure how much other items will attract more guests to my business.

These straightforward requirements make the process accessible and convenient for buyers.The initial setup costs typically range between $500 and $1,200 USD, while annual maintenance fees are generally between $500 and $700 USD.

And feel you'll have more options / strategies to explore with a tri or quad plex in the long range.

This reminds me of how Alex Hormozie describes "the value equation"; Experience in this case is the factor that determines the likelihood of achievement. 1,000%Alex Hormozie is one of the greatest marketers not just alive, but ever. 

Putting it all together: If I were starting over and looking for a house-hack in Denver, CO today, I'd be looking for a 4 bed / 3 bath property in the $500K - $600K range in an up and coming area (like Aurora near the medical campus).

I would definitely factor in some substantial capex/ maintenance and repair costs which could lower your returns.  

Cursory research tells me places like Southland or Frisco have a good upside but we can be persuaded in all price ranges.