Well since I am not from the US I cannot tell you which forms you need with the IRS.
However DJing like any other entertainment business is a business.
As a DJ you are operating a business and hence you have to pay taxes from what you earn as a DJ.
Which leads me to:
When you play gigs, get a contract in place and if that is not possible you need to give the manager an invoice for the money he pays you and you need to file it in your books. So you have to do basic bookkeeping in case the IRS shows up, to prove you paid your taxes…
But for young businesses almost all countries and US states have free counselling on the business sides when you startup. Seek out such a free counselling session and get to know the rules in your country and state.
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