Do you have a list of everything that is included? You know, skimmer, pumps, ATO, lights, etc. If not, get one.
I believe I read that you only have a picture of the empty tank with a little bit of the stand. That's not enough. Ask the seller for photos of everything, you know, all laid out and close ups so you can see the condition. Pics of the stand, inside and out. That shouldn't be too much to ask the seller to do.
You can post all that info here if you want opinions. If the equipment alone is worth the price, go look at it, and make sure all the electric stuff works. Bring it all home and leak test. If the display leaks, well, you still have the value of the other equipment and only need a tank to fit on the stand. If the sump leaks, go to Petco and get an Aqueon that fits the stand and make a sump from that.