After much searching, I have found a person selling Jolla C in my country. I would like to know if the phone is enough so I can use the phone with my personal Jolla account and that the seller does not have to give up his Jolla account to give it to me.

The only advantage of having an old jolla account is the 20percent discount when buying sfosx from jolla store with a voucher sent to the accountholders mailadress. (Or do i miss something apart from few few emails?)

You should make your own Jolla account when setting up the factory reseted phone as it is ment to be individually per user, not per device.