Is selling season tickets a form of self-employment income? A tax expert told me it was, and I'm trying to enter the cash receipts and cost of the tickets in Schedule C.

IF you are in the business of buying and selling tickets, you are self-employed and report your income and expenses on Schedule C.   If you are not self-employed, the income is reported as a capital gain.  To report Self-Employment income and expenses on Schedule C, use these instructions in TurboTax.  

Generally, you are self-employed if any of the following apply to you.

• You carry on a trade or business as a sole proprietor or an independent contractor.
• You are a member of a partnership that carries on a trade or business.
• You are otherwise in business for yourself (including a part-time business)

If this is not your business or trade, then it's reported as Miscellaneous Income. What you received for the tickets is 100% taxable income. What you paid for the tickets is "NOT" deductible from that income.

"I'm trying to enter the cash receipts and cost of the tickets in Schedule C."

If you are not in the business of ticket sales, then entering the proceeds on Schedule C is the wrong approach.

Rather, you are selling a capital asset in which you have basis. As a result, the transactions should be reported on Form 8949 (which flows to Schedule D).