Far Cry 5 > Prepper Stash Locations and Walkthroughs
Stash Mission Start:
There is a note in a box at a stone near Wellington Residence in the south.
Find the mine's entrance:
Go inside the house. There are a couple of boards on the floor. Smash them with melee to find the entrance.
Find the stash:
Go down the ladder and follow the corridor to the barricade. Use some dynamite to blow it. If you don't have any, there is some on the table in the corridor.
Go through and then turn right where the butcher's knife is. There is another barricade straight ahead and one left of it. You need to blow up the one to the left. 2 Zombies will come your way.
The Zombie corridor has two more barricades. One straight ahead, one right. Blow up the barricade to the right.
Enter the little cave with one zombie. There is a barricade at the wall, where water is coming out. Blow that up. Now you can reach the other side, where the green ropes are and where the zombie is / was.
Now follow the last corridor to the stash. There are 3 perk magazines. Grapple to get out. The exit is above the waterfall on the way to the house. Jump into the water.