I hope so the most top selling digital products on internet is camera, laptop, mobile phones and the next comes computer hardware. Of course as you said making money online would also be in the top. Start up the business with digital products. See some sample websites for more guidance.
I suggest these:
(Depending on your skills some of these can be very lucrative.)
1. Stock photos, illustrations and graphics for web usage, such as for websites, banners, illustration of articles. Offline advertisements, flyers, posters, manuals. School projects, work presentations, book, magazine or newspaper illustrations. Software products covers (boxes), CD’s and more.
2. Ready made web templates for professional looking websites for fraction of cost and effort. Users just supply text(s) and web is ready to go.
3. Stock videos and animations for broadcast, advertisements, documentary movies. Also for school projects and education (e.g. medicine / anatomy animations) and other usages.
4.a) Lowpoly 3d models for use in 3d games and other real-time simulations (e.g. military simulators) and real-time visualization projects.
4.b) Highpoly 3d models for high quality renderings. See stock illustrations, graphics, stock videos and animations for idea(s) where highpoly 3d models are used.
5. Textures for 3d modes or other purposes, such as for backgrounds. Tillable textures (can be tilled / repeated infinite times in one or both directions) have greater commercial value.
When creating your online products you should keep these lists in mind <– for good sales.
Think as buyer(s) think!