The Vault becomes available after completing four bundles. Each bundle in the vault simply requires gold to complete, and the item slots are replaced with a large purchase button. Pressing 'purchase' will complete the bundle and deduct the gold from the player's total, provided they have enough.
Completing the Vault bundles, costing a total of {{Price|42500}}, repairs the Bus on the road between your farm and Pelican Town. Taking the Bus grants access to the [[Calico Desert]].