Once you have arrived in Subway Town, you are able to purchase repeating deals from Stew, behind the shop.
Some of the items you can buy can be sold straight away at Jani's Supplies for a higher price. You can, for example, buy Viper Rockets for $66 which can then be sold to Jani for $75. This can be repeated to your heart's content!
To open the console, go to the "base" folder located in the installation folder of Rage and open the default.cfg with a text editor, then put right under "unbindall" in the upper Area "com_allowConsole 1" (without quotes), save. Now you can open the console by pressing the tilde button during gameplay. (the location of the tilde button may vary on what keyboard or language settings you use)
Here are the console cheats:
CvarAdd g_permagodmode 1 = Godmode CvarAdd g_infiniteAmmo 1 = Infinite Ammo CvarAdd vehicle_god 1 = Godmode for vehicles CvarAdd vehicle_infiniteBoost 1 = Infinite Boost for vehicles CvarAdd vehicle_enableAllUpgrades 1 = All Upgrades for Vehicles