Kristin's Altima was a flood car, the guy(actually his ex-wife) I got if from got it with 10-15,000 miles, pulled the interior, dried and reinstalled, had 150,000 on it when I got it, if the Cruze Eco owner drove it 20,000 miles any other bugs/damage would have showed up.
Take it for a good long test drive to see if any CEL come on, test every electronic gizmo you can, like 30+ miles, cause he could clear them just before you get there. It would be good to see the title to verify he's actually driven it 20,000 and how long. He list the VIN so you can probably find out the information through that.
Most big dealers won't sell salvage title, they'd send it to auction if he traded it in and he'd get less money. He say motivated so maybe 6k will get it.
http://columbiamo.craigslist.org/cto/4825357903.html
Clear title Cruze Eco with about same miles for comparison. $10,500
http://stlouis.craigslist.org/cto/4852853959.html
Another Eco with 35,000 miles so $2000 more.