Completing those repeatable missions is an easy way to quickly amass a pile of lunchboxes and coins. From there, you should soon see a mission to "Get 50 Water," or to "Get 50 Food," or to "Level Up a Dweller." You can complete any of these three missions repeatedly, as long as you have not first completed "Equip 1 Dweller With a Weapon" or "Sell 1 Weapon or Outfit" already noted.
Complete objectives from there, until you are asked to either "Equip 1 Dweller With a Weapon" or "Sell 1 Weapon or Outfit." Instead of completing either of those objectives (by claiming a reward), which will disable the exploit, complete other missions until both of the aforementioned objectives are listed. Place the rooms you start with, and have the Dwellers occupy them.
This exploit requires you to start a game with a brand new vault. Submitted by: nukeboyy Infinite Lunch Boxes and Money (Exploit) The rocks should still be gone but you won't have to pay for their removal. Now go ahead and place the building wherever you like. Instead of selecting an empty space, eliminate rocks until you have almost no money left. Next, you'll need to choose where to place it. Submitted by: sanguinious Affordable Rock Removal
Any dwellers that were sent after him should now have legendary items in their possession. Quickly look to your first dweller to see if he received an item.