For this achievement you will need to hold up all 20 stores ONLINE! There is a total of 20 stores you have to hold up scattered around Los santos. You can find them all on your map, the ones you've already robbed will have a green check mark on them. Before entering a store to rob them make sure you HOLD
and equip a mask so they don't recognize you when you go back next time to buy snacks.
Start in one area and hit every store in the area your in, like don't scatter around and jump from one side of the map to the other just to hit the store, work your way up to the top stores in your map so you don't have to go back and fourth.
GOOD LUCK TO ALL !!! MESSAGE FOR HELP!