A few approaches:
1. Using the standard network render: no, can't be done
2. Using a complicated VPN setup: the last I heard of this was "maybe," but I've not personally seen it tested. Anyone else?
3. (Not really net rendering) Using TeamViewer: have regular Maxwell open on various computers, with local files on each machine. Just use TeamViewer to connect to a remote computer, and hit "render" on that computer. There's nothing really networked about this, besides remote control of a machine. However you can incorporate Dropbox to start sharing dependencies between machines, or to gather your output files in one place.