The first thing all inventors should know is that they do not need a prototype to file for patent protection.  Many inventors mistakenly believe they need a working prototype prior to filing for patent protection.  However, prototypes can be useful when determining whether your invention will work properly.

If you plan to license or sell your "patent rights" to your invention, there is no need to build an expensive prototype unless you need to determine if your invention will work properly.  Obviously if you are going to manufacture products under your patent rights you will need to design a working prototype prior to manufacturing the product.