Maybe consider refi'ing and harvesting some of the equity out?

In my experience, most of the org's that I work with have very little housing resources and yes, the harvest is plenty when it comes to tenants.

If he doesn't get that price he will just continue harvesting cash from the property and postpone selling. 

What is called the "lazy mans 1031" where the extra depreciation that @Shafi Noss was talking about is harvested. 

What if China invades Taiwan, what if China nukes CA, what if E.Warren declares yes she actually is a Reptilian Over-Lord here to harvest humans, what if what if what if. 

I do plan to take advantage of harvesting new properties from existing properties as much as possible, but fear that will only get me so far...Curious what other options are out there?

I think you could legitimately use your SDIRA to buy land and have someone plant trees and have them harvested every 10 years, you could invest in a syndication where someone else manages the properties, or you might be able to get away with buying a self-storage and getting paid a reasonable salary to run it. 

In the progress of weeding/ harvesting equity from duplexes which are good- but not great cash flowers.

In order to find low yield investors it will take some DIY elbow-grease whereby you would need to get in there and cultivate and harvest your own SDIRA investor-leads outside of pre-programmed, SDIRA meetups. 

The Mills they would never do that otherwise they get black balled and no one will deal with them.. but johnny lunch bucket logger... they would cut you out in a heart beat. however most owners would honor the sanctity of contract even though there was no laws or rules pertaining to timber harvest contracts....