Don't forget, if you are selling anything on eBay, you can then get into business deductions. Whether or not you get a sole proprietorship / DBA, everything you buy is deductable as well as the space you use in your home for the business. I have a Paypal business account and use the debit card for postage and purchases - even household purchases - and end up getting cash back which offsets their fees. And, of course, the fees are a business expense and deductable!
As for the level of reportable income, it might be $750. It is for most affiliates, mystery shops, etc.