Hi there and welcome
It will depend on the issue, do you have access to the camera at the moment so we can try some things?
thanks, ***** ***** is a general error, but often the cause of the error is lens communication. This could be for many different reasons. For example, if the aperture assembly on your lens is broken and needs to be replaced, the camera will tell your lens to change the aperture, the lens can’t because the aperture assembly is not functioning, and so the camera will not have any confirmation that the lens obeyed it’s command.
You can try the lens on a different camera then see if it works which confirms if the lens is the issue
IT can also be dirt on the contacts or a faulty memory card. These problems are very cheap to fix and it's worth purchasing.
But if the problem is not this, it is then the mainboard in the camera, in this instance it would not be worth the repair as it is going to in the long run cost more then the value of a new camera.
It is a gamble, its a very good camera, but the chance your in for repairs costing more then the value of the camera is quite high as I am sure the original owner has already tried a different memory card, lens ect.. It would help if you could ask them, else it is probably best to avoid the purchase.