Is there anything illegal about building computers and selling them on Ebay.? -

You will need to establish a business, and pay taxes on your own income to make it legal. Make sure you charge sales tax if you re shipping within your state. You will need to apply for a state sales tax permit, once you establish a federal tax id.Fed tax id:http://www.irs.gov/businesses/small/arti��Then contact your state and apply for a sales tax permit.