C4D render net, buy the version which matches the number of future machines.
Again, not so difficult. The machines need to be on an ethernet, you start a small application on each one (C4D server software), on the host you start a web browser (Safari, Netscape or whatever). The browser local webpage allows you to point to the source files, and where you want the output files saved. Then you start the job, it looks and sees the various servers, distributes the data between them and before you know it all 5, 6, 8, 10 machines are working on the same animation. Each machine takes a number of frames and renders them.
You can mix Mac and PC. It's the two heads are better than one theory.
Mark