Let's face it...commercial lightboxes are expensive. But as an artist, it's hard to do without one. I was able to construct a good sized one on a shoestring budget. I obtained a large glass cutting board (it is tempered glass so it will hold up if you are a little heavy handed with your pencil), three small fluorescent lights (13 inch i think) that you can link together, masonite board, furring boards, stick on velcro, wood glue, and some nails.
Cut the furring boards into 4 pieces to make a square the same size of the glass cutting board. Drill a hole in one side for the plug. Nail them together (carefully...I cracked a board. Might be better just to glue them instead). Cut the masonite board to fit, and glue & nail it to the back with tiny nails. The lights and the glass board are held together by velcro, so if there is any problem you can take the glass off to replace the lights. All this cost less than $50, and it's a honking big lightbox!