I've always rented rooms or small apartments, and have been happy doing so, because it requires so little time and effort to maintain on a daily basis (allowing me to pursue career goals and hobbies). 

Stock market (index funds) return an average 7.5% adjusted for inflation so I believe if you're doing REI, at least shoot for something higher than the market. 

The publicly traded ones trade with the same volatility as stocks.

When hotel stocks and airline stocks are falling, it will be hard for AirBnB to convince investors that they're different.

I will maintain your unit to the highest standards and guarantee payment every month on time. 

A less than desirable outcome would be to limit CAPEX to maintain a 8% ROI.

Don't put at risk what you need chasing what you want.The stock market has hundreds of years of history of showing positive gains. 

Two dishwashers, some lights, screen enclosures, some inoperable cooktop units etcMy Estimates (note that the market CAP is 7-8%):- WORST case scenario for rents ($1225), occupancy rate (88%) and high repair costs ($75K): 2.3% CoCr and 5.1% CAP - BEST case scenario for rents ($1300), occupancy rate (95%) and low repair costs ($20K): 7.6% CoCr and 6.6% CAP rateEven though I strongly expect the numbers to look closer to the best case scenario above, considering my out of pocket expenses are going up with all of the repairs and also that the stock market is tanking right now and money is becoming scarce, I'm not so sure about this deal.

But that's OK, because my 401k is earning 9.325% on the loan (more than it would earn on average in a typical stock fund).

You would likely get a better return on your capital simply cashing out and putting the proceeds into a stock index fund like a Vanguard S&P 500.