Check out  EverBooked ,  Mashvisor , and  AirDNA for some very accurate and cool data to gain more certainty on Airbnb rental predictions.

Here is another data point to consider -- the yield curve.https://www.nytimes.com/2018/06/25/business/what-is-yield-curve-recession-prediction.htmlIf the yield curve is predicting a recession, the economy will slow and some tenants might not be able to pay their rent.

And I predict that it will continue to grow.

My view is both those owners got lucky but maybe they accurately predicted a lack of near term appreciation. 

I didn't even think MTM was favorable for the landlord before I moved from Canada because it would (in my mind) create havoc in terms of predicting your future cash flows. 

Either way you can’t  predict those dynamics and purchase and sale transactions in my opinion should put a lot more weight on price.

I do not plan to predict when will the market turn down, nor will sell anything before it actually turn down.  

If there are no comps I would predict an appraisal problem which will lilely lead to a forced price reduction when it is under contract.

Their income and expenses and problems are pretty predictable.  

We're not talking SF-over-the-last-10-years appreciation, but I'm interested in predictable investment returns, not gambling.