Since this is considered self-employment income, you will have to pay Social Security and Medicare taxes on the income at a rate of 15.3%. If you have additional income to add to this and you are single, anything over $10,400 is also federally taxable.

Since you sold items, you only need to pay profit on your gains. You can create an inventory of what you sold and as best you can, what you paid for it.

You can also deduct your internet fees and any website should you have one. If you bought your computer in 2017, you can depreciate the business portion of it.