Is Gambling the only option that can provide quick money

Is Gambling the only option that can provide quick money? No is the answer to this question, as for me, I don't really think Gambling is the only simple and reliable option. Besides it is a game of luck, many people believe that they can get huge amount of money from it with out loosing, they believe if they keep trying they can be lucky to win triple of their money, which is not a reasonable idea to think of.