Clan castle rebuild gold boost
So I recently convinced a friend of mine to start playing CoC, but as he is now level 9 he wants to join my clan, but his clan castle is still destroyed. There is an option though (40000 gold) for me to rebuild his clan castle, or am I wrong? I press the button, with both of us having idle workers, but nothing happens. This seems to be a nice way to get people started with clans, but how does it work?