hi Alley

you do not have to have an abn to open an ebay store

regarding taxes, ALL ebay income, big or small, needs to be added to your other incomes, wages, etc. and declared at the end of the year.

you cannot 'earn' money from one source (ebay) and say it is below tax threashold, if you have other income, when all added together would be a taxable income, doesnt matter if it comes from just ebay sales or ebay Store.