In single-player, "cheating" is a personal definition. Here are two perspectives:
For those who don't want to use someone else's save, the "Extra Options" mod is a popular alternative. It allows you to toggle a single line in a .ini file— UnlockAllThings = 1 —to make every car in the game purchasable from the start of a brand-new career. nfs most wanted save file all cars unlocked
