Getting ready to build a shop- first time in many decades I have done so- perusing this forum for ideas.

Sounds like you're on the big island. If the Mongoose would kill the rats, they would earn their keep....lol. If I remember right, there are no snakes in the islands, so the Mongoose have no enemies. Those are some mean critters though! Good luck on your build. I can imagine it would be a challenge out in the sticks on that island!