The only way to find out about hidden hets, is to breed with different morphs. Unfortunately, you could be test breeding for years in order to reach the conclusion that your current snake has no hets.
Your best bet to test to hidden hets would probably be a Snow - that has a combination of Amel and Anery, which would be the hets that a Normal is most likely to be carrying. However, Amels, Anerys and Snows aren't valuable and there would still be a lot of Normals in the clutch. On the other hand, your Normal could have no hets at all, in which case breeding it with a Snow would just produce a clutch of Normals.
If you want to produce valuable morphs, then you need to go and buy different breeding animals. Do some research in advance - decide what morphs you really like the look of and which will sell well in your area (I don't think you'll be able to ship them outside your area until you're 18), then buy the Corns that will give you those morphs. Unfortunately, as you're looking to produce valuable morphs, the Corns you buy will be a lot more expensive than your Normal was.