Schedule C
The Federal tax is easy - just a schedule C....no Tax numbers needed (other than your SSN) unless you have employes. No problems if you show a profit. If you show a loss, the tax law says you can't claim it if it is a hobby. Business is defined as activity carried out with the intent of showing a profit....you do not have to make a profit but, if audited (you probably won't be), you need to convince the IRS that you intend to. Here are some things they look for.
Separate business checking account --- or a separate way of tracking business expenses and income. Like Quickbooks or Quicken Home and business.
Separate business Credit Card --- I use PayPal and a PayPal Credit Card for mine...no personal purchases on that card.
Accurate accounting....Save all your business bills. An alternative to this is to make all your busniess purchases on the separate credit card and save any online copies of bills.
Have a business plan.
The States vary widely....Delaware has no State Sales Tax so collecting sales tax is not a problem. But, you do need a business license and we di have a gross receipts tax.
Most states and many localities have a sales tax and you'll need to establish a sales tax account...how tough they are on enforcement depends on the state. And what level of total income you have might affect whether or not you need a special bank account to hold sales taxes in.
I never collected NY sales tax on my small business receipts and never ran afoul of the revenuers even though I had to file state income tax and my federal schedule C was attached.
Some states require sales tax collection on casual sales, others do not.
Take a close look at the Sales Tax rules for your state...some of them are almost sensible, NC might be one of them.