Don't really know anything about the hay buster brand but a quick search on land pride and that's about 1/3 of the price of a new 6 footer.
Needs some new bearings and packing wheels so? And being a rental unit for 7 years means it could have been abused.
I'd want to look it over good and check the chains and sprockets for wear, but compared to new that's not a bad price for a 10 foot pull type.