The fact that owning the bricks and mortar is actually a liability not an asset as equity grows and ROI diminishes to the point of no longer keeping up with inflation. 

ROI is very low and will only diminish as equity, appreciation builds.

When there is a lull of any sorts investors pick up the slack and any surplus inventory diminishes.

As you mentioned there is still a decent supply of NPN but do you see that inventory slowly diminishing with a full circle back to the focus of seller financed notes for investors interested in cash flow?

The career field will not diminish, but the strong and smart players will have to adapt to stay ahead, and will likely become adopters of the new infrastructure. 

The random example I like to use is male testosterone.

A good Property Manager is KEY to beating the odds of failure].The common consensus around BP is that most markets have a pricing "sweet spot", below which cap ex and other expenses tend to wipe out your cash flow over time, and above which your cash returns as a percentage of your outlay start diminishing exponentially.Hence the invention of phrases like the "1% Rule" (rather than the "2% Rule"), and the many threads that will try to tell you why 12% gross rent per year will be better than investing in 24% gross per year (which looks wrong on paper).

Remember, if values hold steady and rent stays flat, the purchase power of that money will diminish due to inflation. 

3) Does she have "diminished capacity" (is she mentally capable?)

As a previous TK investor myself, who has seen prices rise and good TK opportunities diminish, for my own buy and hold investments of late I have turned to a investment strategy that allows me to invest in property - usually syndicated portfolios of 10 SFR, but also now apt buildings - that remain co-owned by the seller/managers.