A formal assumption of the loan may be the right strategy here depending on their level of motivation and all of the circumstances.

If it doesn't sell and I'm motivated, I'd lower the price.

This equates to more motivation for them to pay and more options for them should they get in a financial bind.

He was of course incredibly convincing, has mastermind meetups, and seemed very genuine, but at the same time seems to be a very good salesman.

It's just that you have to have 2 folks with the same goal and motivation level to get it done.

remote BRRRR is incredibly difficult.

Subject to sales were a lot more popular when interest rates were 15% +( 1979-1983), there were no “due on sale” clauses, and few real estate transactions were occurring.However, there are still some benefits to the seller in particular situations if (1) the seller understands and accepts those risks and (2) certain safeguards are utilized to modify some of those risks.A few possible seller motivations for selling subject to1.

having an incredible onsite manager, adding colorful flowers to perk up the curb appeal, paint the windo shutters to make them pop and renovate the interiors.

Might be more motivated to take a quick sale lower offer. 

Your experiences and insights are incredibly valuable, and I am eager to learn from those actively involved in the market.