The warehouse is a place where Chaos Insurgency and Class-D can rob shipments for a set amount of cash depending on how many shipments they rob, each shipment sells for 75 cash. The max amount of shipments you can rob is 7, which sells for 525 cash. After stealing the shipments you need to sell it to Barry, who is in the CI Tunnels. For a guide to rob the Warehouse see the video below.
https://www.youtube.com/watch?v=LCpe5gS2Lcw (Video by Bananan Gamer2)