My Red Flags:

1) No pics in the ad. Or only one. Or one taken at night, or from the window of your apartment 50 yards away.

2) No text in the ad. “For sale” and nothing else. On Craigslist. Not charged by the word.

3) Surly asshole of an owner. If you can’t be civil, I can’t deal with you

4) Lying. Car “books” for $4800. Yes it does. At a dealer. With all options. With lower miles than this car. In pristine condition. I can check this on kbb in minutes. People that do this are habitual liars.

5) Lying II, by Omission: When I start the car, the dash lights up like a Christmas tree with warnings. None mentioned in the ad or messages.

6) Incredible ignorance. “Needs head gasket, but only $20 at Autozone.”  It’s tempting to call these people liars, but mostly they are just utterly ignorant of what is under the hood.