Hello, good question. It really depends on how accurately the prototype needs to be. The first thing you need to check is that you've taken into account the design guidelines for producing something for CNC. There are a few things to consider for this, namely no overhangs, considering what type of bit they'll be using. The CNC place should give you feedback on this, there's also a few online resources for checking your design - pretty sure there is a good guide here: https://geomiq.com/cnc-design-guide/ The next thing you need to think about is producing the engineering drawings, this basically acts as a contract laying out in numbers what dimensions the supplier must achieve. Finally make sure you try and pay via a platform like alibaba that covers you for any dodgy companies that take your deposit and don't come through with the goods - speaking from past experience! :) If you want to schedule a call I would be happy to help set up your engineering drawing and help you get the best price using these online platforms. Cheers, Alex