What’s the saying? No good deed goes unpunished!

[JMBT]

Trying to help an older couple get their truck running good enough to sell. They are good long time friends of my brother. The man found out he was sick a couple years ago and they quit trucking and sold their truck and trailer. (At that time it was immaculate and had been freshly inframed). The person who bought it did so on owner finance terms with a very small down payment, then proceeded to tear the living hell out of the truck in every way possible. Inside, outside, mechanical,....you name it. When it became too much for them to keep it going, they abandoned it, truck and trailer, way across the country from where the owners live.
The truck sat awhile in poor repair and another person who had an eye for it contacted the old couple and stated he had no money for a down payment but would pay for all the repair costs/tow costs if they would owner finance it to him. They decided to go ahead and try it again, thinking what would be the chances they would get f$cked again.
It appears this second person actually tried, a bit, but was either too lazy, or stupid to learn how to wrench on the truck himself, and therefor had to rely on the shitty shops and stealershits for the repairs. He lasted and even shorter time then the first person. Ran out of money, and abandoned the truck, not running, with a $3800 shop bill even further away from where the old couple live. In tears the old lady called my brother, a long time friend, and he payed one of his buddies to tow it to his ranch so we could take a look at it for her.
Of course we are not charging them anything for the labor, but they plan to buy whatever parts we need to get it in shape to sell.

Long story short: today’s disaster. We pulled the can down and popped it apart and here is what we found. I really don’t know what to suggest to them at this point. I know they don’t have the cash to buy a new DOC and DPF, plus all the other parts that will be required. I would suggest they demandate it, but that might make it hard to sell??? What do you guys think?? (First two pics are the DOC, last is the DPF)