From EncyclopAtys
A guild is not supplied with a Guild Hall upon creation. It must be purchased by going to any of the guild apartment caretakers and purchasing it for 10,000,000 if in a capital (Yrkanis, Fairhaven, Zora, Pyr) and 5,000,000 in other towns.
Once purchased, all members of the guild can now access the guild hall and its inventory by going to the city where it is located and entering through the correct door.
The guild apartment is large and includes sevral rooms which may be used for role-play purposes.
All members can deposit items, but only senior officers and the chief can retrieve items (and only if they are subscribers).
Not to be confused with the Guild Island.
Now (June 2024, with Patch 00994), you are able to expand your guild's inventory by building chests from your guild island.