Hyper 7's are pretty good buggies, but they are a bit outdated so keep that in mind when considering the purchase, in other words dont pay too much you can get a new rolling chassis for about $175. Main thing is what kind of engine,pipe,electronics come with it. As far as wear the most expensive thing is cvds so check to see if they are worn alot and if they are bent.
For what it is worth I know a guy who has one with only a few races on it and he bought my old one which has the yannick conversion and all lunsford turnbuckles on the front. If your interested PM me and I can give you his number, I doubt he would need too much for them both.