Determining the condition of used bikes is really dfficult from photos or quick visual inspection. I've bought some on Graig's List that looked decent in the photograph, but later turned out to be not so good. Alternatively I've also bought some that looked like crap and after a good cleaning, turned out like they were brand new. It seems like you have to spend a few hours cleaning and readjusting just to figure out what you got.
I agree with Artkansas writing about the lack of description of the model as a warning flag. But then alot of owners don't really know that information, especailly the older the bike. My frame of reference is that I was purchasing old bikes to fiddle around with and maybe build a fixie. It seems you are intending to buy one bike that you want to ride as soon as possible. That higher expectation is going to make it more difficult.
I guess one thing you could do is get a chain wear guage and check for chain stretch. If the chain is too elongated, it's been well used and you may have to replace the cranks and rear cassette. Another thing is to check for switched components. You probably don't have a database to check the original equipment of one years model (nobody does), so this too is difficult. But check to see if the front and rear tire rims match. I've had that happen once where there was a 10 speed rear wheel was put on a 12 speed rest of bike frame. Didn't notice it untill after I cleaned it up a bit at home. But it was only $20 and I just wanted it for the frame. If you can determine if the brake pads are original, check to see if they are worn down or not. Well worn indicates more use and wear and tear.
Good luck with the bike. The listing has been taken down.