The keys don't work at all? Might be the symptoms of a bigger problem, like liquid spillage - meaning the whole thing could take a dump from corrosion soon.
I'd only do it if it was local and you had a chance to boot it up and see it work for yourself. But like others have said, this does sound suspicious, so proceed with caution.
But if it is a local deal, and you can boot up the computer like the posters above said; then hell yes, I'd say it's quite worth it. (Hopefully it's not a spill damage)