That's the golden rule for any financial venture including buying corn commodities. Corn is one of the world's most widely farmed crops, in part, because corn is needed for foodstuffs, plastics, and biofuel around the world. That makes corn a good investment and a fairly stable one. In order to buy corn commodities, often referred to as futures, and make a profit, you'll need to take into account how a variety of real world factors might affect prices before you actually go through the purchasing process.