Not really. If you have a geek, just start shopping for deals on hardware (pricewatch.com is a good start. If there are any in the area, computer shows are another.). You find a set of deals, you grab and store in the box until you have the parts you need. Render node specs do -not- have to match your main system specs. All you need is OS, maybe a video driver, and the remote render software. All the hardware you need is motherboard (with onboard video), CPU, hard drive, power supply (350 to 450 watts), and case. You can also toss in a super cheapo DVD player to load with, altough if you want you can also transfer installation software from a DVD to a large enough flash drive and install from USB.

Forget the audio; turn it off in the BIOS and don't install the drivers. You can do an SSD if you want, as you can get a 500gig HDD for $50 or less (with a 3 year warranty), that would be for geek points. Don't waste your money getting a brand name; build them yourself and you will get out a lot cheaper. You will also be using industry standard parts, so getting replacements will be simple (Keep a few of the CMOS batteries on hand; most motherboards use the 2032 buttons available just about everywhere, and a cheapy video card or two (and by cheap I mean $20) on hand; motherboard video tends to die at odd times, and having a solution to plug in and go saves time).

All you need to control that is a 4 port KVM switch for whatever mouse, monitor, and keyboard you use.  OH, and a 5 port gigabit switch. The vast majority of motherboards with onboard ethernet are gigabit now, and it is worth the cost of the cat 6 cables (about double what cat 5e costs) to get the extra speed.

 

attached is my first rendergarden, built just that way (only the ethernet was 10/100), old CRT on top, built on one of those $30 printer stands.  The first upgrade there was putting a swing arm on the left side, and mounting a 17" LCD. Stay at least a generation back, and you can get incredible deals as warehouses make room for the new stuff......