That ad is for a 3 horse not a 4 horse.
I am looking at the pics on my phone and not a computer and it doesn't seem to be in the best shape. Could be just dirty. That ad looks to have been there for a while and they reduced the price, that tells me that they are/were asking too much for the condition or area they are in. I would call them and talk to them about it, get a feel for how big of a hurry they are to get rid of it and see if its worth making a drive to take a look.
Just from looking at the pics on my phone, I wouldn't pay $8900. I would low ball them a price depending on how fast they want to get rid of it and what exactly is wrong with the trailer(to figure the money you will have to spend to fix it)
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.