The Frankentype.  You may have built one already and don't even know it.  This is the prototype where you've snuck out to the graveyard of broken products and spare parts.  You've used glue sticks and duct tape.  You've put it all together with blood, sweat and that idea that struck you in the middle of the night.  The result is a prototype that only an inventor could love, but you've taken that first important step of prototyping in the right way - you've built it, you've proven that it works and most importantly: you haven't spent a lot of money.  

 

And you should expect several iterations of this cheap, ugly prototype, as it is a low-cost way to understand your future product's functionality, and prepare you to make it's prettier cousin: the MVP (minimum viable product).  This is the one where you'll start a whole new iterative process as you begin your market validation, and gain valuable customer feedback.