Guild Wars 2

what happens when you pay for the expedition for the other guild hall?

… just a question

You can not have two. If you do another guild hall then it change to that and upgrade transfer.

https://forum-en.gw2archive.eu/forum/game/hot/Day-Six-Guild-Hall-Statistics/first#post5679436

1) No, you can only won one at a time
2) Yes, to capture a different one go purchase the expedition for that hall and complete it. You will retain your old hall until you succeed the new expedition. All of your upgrades will then apply to your new hall and you will loose access to your old hall.

thanks for that