Open the mission file (e.g. "Data/Missions/M02.ini" for Mission 2) and search near the end for lines beginning: "Act_AdjAcct = " Just edit the one that adds the reward money to a higher value. For example if the reward for mission 2 is 16000 (just a guess) then search for "Act_AdjAcct = 16000" and change it to something larger, like "Act_AdjAcct = 125000".
