And working long hours every week forever is not sustainable, without damage.  

And before all run to google and freak out, it's been happening for a considerable amount of time, the Fed as primary buyer for the securities, which include how the U.S. dollar and Gov. as a whole sustains life actually. 

Not enough Retirement homes, not enough workers, pay scale is not sustainable. 

I see it'd be more likely that we'd have a sustained period (5-7 years) of steady or slightly declining prices.

I believe 3% to be a healthy and sustainable rate of increase.

On another hand, with a buy and hold rental property for cash flow if the market crashes your more likely to sustain the wave.

I understand that landlords desire a "free" service, but running a business does involve real costs, and electronic rent collection does involve both fees and risks - and all of that has to be paid to have a long-term sustainable business.  

We focus around local sustainability, and you benefit from living with such knowledgeable, go getters. 

In our local markets we like to look for the downtrodden and unloved as they offer the best opportunity for forced appreciation (read: we can pull our initial capital back out once the property is stabilized).They also allow us to rehab the property to our standards for energy efficiency, sustainability and healthy environment without the cost of undoing the work of a recent renovation.In remote markets we are struggling between our nature to say - the bones are good, lets' go - and our trepidations around managing a renovation 1000 miles away with a team we do not know.  

While with large commercial property, the income of the property is at the core of the qualifying parameters, you, as the manager, have control over the success and sustainability of these revenues.