I think you can easily use multiple PCS with cloud computing. All you need is the person to manage the network. Many of cloud computing companies are using the same successfully.
Hi TweakingKnobs - the free service the answer was given already by kastoria.
The commercial solution could be our renderfarm www.renderflow.com
The advantages of a commercial solution are confidentiality, service guarantee and speed.
For testing of our service you can visit our Demo account. It is public, you can test, compare or share your projects there.
For confidential render you can register to a private account where you receive a test credit as welcome bonus.