Design a product using 3D modeling software like SketchUp or Blender. With an initial investment of under $5,000 you can start your own small fabrication business or pursue product design as a hobby. A 3D printer costs around $750 and is a tool for prototyping designs. Share prototypes online to find manufacturers on sites like Alibaba.com for small batch production. Market designs freely using social media like MySpace, Facebook, Twitter and Foursquare to build an audience. Sell finished goods on websites like eBay or Craigslist to reach local and national customers.