"Ran great when parked" or "runs great needs fuel pump" are always dismissed.
I could careless about the body. Be realistic, the car cost how much and where do we live. Actually I am more concerned about something that has "fresh paint" then something rusted out with stock paint.
Anything that has close to 300k and says something like "runs like a top" always gets a laugh.
Come on though be realistic. Most of the cars that have descriptions like above and in the previous post are very low cost cars. They should have issues on top of all the factory issues associated with the car.
If you spend $500 what kind of car are you realistically looking to get? Good chance if you toss another grand at it you will have a decent runner to get you around for a few years until it goes and you need to buy another. No one wants to buy that car for $1500 though and the seller will know they will loose there butt if they toss the cash into it.
I have used the term "mint" before. I was selling the car for $8500 and took $7900. The car had previously been fully restored (professionally) and I bought it way below what it was worth. I drove it for the summer then sold it way below what it was worth. I am not greedy, if I get a deal I will pass it on. My definition of "mint" means no mechanical, paint, interior, non OEM, or other defects to speak of.
The term "mint" and "showroom quality" should be equal. If your ride would look out of place sitting between a two similar types of rides that are "showroom quality" you have no place using the term "mint".