Shop Crates is a multiplayer mod that adds shop system that allows players to create their own shops.
After placing the shop crates you can configure a trade by selecting the item you want to receive and the item they want to give in return. You can also set how much you want of that item. (Can't trade Enchanted Books and Enchanted items due to a bug)

Once the trade is set up, the player who configured the block becomes the owner of that block. Only The owner of that shop can acces the storage.

If anyone else opens the shop it will open the trading menu. Everytime someone buys something it will take from storage and the item you want goes to "Earned" slots. Earned slots are bigger than 12. When earned slots are full it will store how much you earned. When slots are empty again it will move those extras into visible slots.

Also be careful breaking the shop crate because it will not drop the items inside. If you are the admin take all the items inside before breaking it.
To prevent anyone else from breaking it you can put traps in the owner shop menu.

There is 3 traps. You can put these traps into the slot on the left of the text "Earned".
First Trap is tnt trap.
You can craft 4 tnt traps by 1 tnt and 1 observer.
When tnt trap is on the block when anyone other than owner breaks the shop it will explode and deal 300 explosion damage.
Second Trap is Carved Pumpkin
If you put Carved Pumpkin with Curse of binding enchantment. It will unequip the helmet and put a Cursed Pumpkin into his head.
Last Trap is curse of Thief
When broken while this is on the slot, the player gets an effect that last 2 hours. While effect is on player can't open any interface like chests, inventory, crafting table ect. Including chat and settings.