Now that rate is not sustainable, but 18% (1.5%) is in the short term (12-24 months). 

I am not speaking o the longevity, viability or necessarily the life span. just saying why not use crypto currency for acquisition of assets, you can be anonymous and enjoy a continued and sustainable way of building and holding wealth.

;)"Won't near-record unaffordability levels make it difficult to sustain these prices, or cause a reversion if it continues?"

Take away their JOB and nothing to show for it or withstand a storm.As we all know different locations and lifestyles require a different amount of money; I believe that the idea should be to build enough "cashflow" to sustain and (over time) expand they lifestyle we are familiar with. 

Cause debt  is so costly, so literally telling you less leverage to keep this investment sustainable.

Because I bought the property as an FHA home loan with 3.5% down in order to refinance it to generate sustainable cash flows I am having to put down about 7% down (the home currently has about 10% equity prior to the refinance) so this additional investment should generate about 20% return.

If you keep reinvesting the seed investment money, the ROI can be more than 100%/month, or even week, though it is not sustainable for all 52 weeks due to the fact that campaigns have a natural life cycle.

Bottom line is sustainability, and running most your businesses almost on autopilot with as little overhead as you can.

The risk profile (if there's even such a thing)  is better diversified since I'd be able to own 3-4 houses vs 1 house in the Bay or SD for that price (feels like putting all my eggs in 1 basket)3) Appreciation - I 'feel' that the Bay are house prices are not sustainable in the long run (10,15,20 years) and even if home and rental prices continue their meteoric rise, this is an area saturated with big money investors that are able to throw down all cash.

The current trend doesn't seem sustainable as wages in the area have not kept pace with the rising cost of living.