If you want to get loads of money in the game, simply get your men to complete the first mission then enter them in the last. As soon as they appear, get one of them to search and collect the money if there's any there. Then simply leave with the money via the staircase. Keep this up until you've got enough money to buy the necessary equipment. You can do the same sort of thing for the artifacts that you can get during the game. Enter the mission, find the artifact and then get out. Now just go back to the same mission and get someone else to pick up the artifact in your question. This way, each of your characters has the top of the range weapon and armor.