But accompanying a more measured tone was also the noticeable maturation of thought around the still developing SFR and BFR asset classes.

You are focusing only on the IRR which is not a valid measure because it only looks at the return on premium.

A measurable portion of his returns (plus or minus!) 

Review your state's landlord tenant laws and enforce any measure regarding non-payment of rent.

What key performance indicators (KPIs) do you track to measure their progress?

This will always result in conflict and uncertainty, because were measuring apples too hand-grenades. 

2) What protective measures should I consider as a buyer in a seller-financed deal to ensure the offer is as efficient as possible?

It's an effective temporary measure to buy a small amount of time to figure things out but its like poisoning the well, it will have long lasting effect on your personal credit and dismissing the BK won't change the credit impact.If you are doubting the validity of the lady's claim to the property, file a quiet title action and have her prove it belongs to her.

Literally he had to call in help because he wasted hours trying to figure out hot to install a deadbolt on the new doors, forgot to take the right measurements, had to go back twice, raised his price a little on the job, and I could go on and on.

Obviously I can picture it, but I don't know the exact measurements.