If it's casual activity, it's hobby income, although you must have sold large lots to reach the $600 threshold.
You can report hobby income under "other income", report the difference between your selling price and your purchase price. If you sold at a loss, don't report it as Income. The IRS may send a letter asking for an explanation, you would reply with details and proof (that you sold items for less than your cost, etc.)
Or report the business activity as a Schedule C business. Just follow the steps in Turbotax online and answer the questions in order. If you want someone to hold your hands as you go through it, you can upgrade to the Live online version which gives you a CPA agent via chat to help you walk through your situation.
There's no jail here, at worst the IRS will tax the entire amount of your sales if you can't prove that you had deductible costs that reduced your profit.
@VolvoGirl ???
