Maintenance for the week of November 11:
• PC/Mac: NA and EU megaservers for patch maintenance – November 11, 4:00AM EST (9:00 UTC) - 9:00AM EST (14:00 UTC)
• Xbox: NA and EU megaservers for patch maintenance – November 13, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
• PlayStation®: NA and EU megaservers for patch maintenance – November 13, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
I know I need 10 players to be able to access the guild bank, but does it cost money or do I just have to keep at least 10 members for the guild bank to work?
You need to have and then hold 10 player accounts memberships minimum. If you fall below that minimum, you will no longer be able to deposit items into the guild bank. Withdrawing items will still be possible but you won't be able to return them to the bank either.
I don't recall there being a fee to open the guild bank account.