Can't figure out how to set up a render farm?

A friend of mine does some pretty intense graphical rendering using Cinema 4D on a Mac running Snow Leopard. He has an i7 quad core processor and has 16 GB of RAM but it still takes up to 15 hours sometimes to render his weekly videos. He is good with graphics but doesn't really deal much with any other aspects of computing, and says he looked into setting up a small render farm (just adding a single machine) but couldn't make head nor tails of how to do it and asked me to help him set one up.

What is needed? Can I use a Windows machine as the secondary machine or does it have to be Mac as well? How exactly do I go about setting it up? Thanks in advance for any and all help you can give.