Unable to complete setup of used Ipad
This is the DEP enrollment screen. Contact the business that manages that device to either return it to them or have them release the device from management. Only they can release that hardware by Apple policy. 

If you don't want to hassle with a potentially stolen iPad, contact eBay to see about a refund or how they handle sales of goods materially different than advertised. (on the assumption you didn't bid on a locked iPad)