If you're looking at installing a large number of render nodes in your home, you need to consider both power and cooling. We’re talking about multiple systems sitting in an enclosed space, which will consume a lot of power and generate significant heat in a very small area. You should consequently think about how many nodes will fit in the space allotted.
For a freelancer using a home studio, you may actually be tempted to build 10 identical boxes, but keep power consumption in mind. The electrical standard in U.S. homes is 110 V at 15 amps, which means 1,650 W is the maximum for a typical circuit. Some houses may have 20 amp breakers, which gives you a little more leeway, but putting 10 nodes on a circuit means you'd better build extremely efficient systems. If someone turns on a hair dryer on the same circuit, you'll hear the breaker flip pretty quickly.
If you really need to put 10 nodes in your home, you may want to split them up into two groups of five. Those five may still consume most of the power available to the circuit they are on. However, keep in mind that with a low thermal design power (TDP) processor, these systems should only consume about 140 W of power apiece at 100% utilization, depending on the actual processor used, motherboard, chipset, and hard drive. Across 10 systems, that’s 1,400 W, which is still very close to the maximum yield of an average household line.
After power, your next concern should be cooling. Several 1U computer systems placed in a tight space will generate plenty of warm air behind the boxes. In order to boost airflow efficiency, most IT departments maintain a hot aisle/cold aisle layout. With a hot aisle/cold aisle layout, the systems draw in cool air from one side, which is then exhausted out the other side. To a lesser degree, you can apply this data center concept to your setup at home to handle the airflow for several nodes. Make sure, for example, that there is cool airflow at the front of the systems and a way to evacuate the air behind them (don't put the back of your rack against the wall).
You also need to worry about redundancy. If one node goes down, you could potentially lose that portion of your render farm. If you can spare the expense, you could build a spare node to swap in as needed, but then you have to suppress the urge to use it as a node and defeat the purpose of having it as a spare.
With multiple render nodes, it is important host the files for your software somewhere else other than on your production workstation, especially if you're trying to use the workstation while the other systems render. It is thus a good idea to either buy a network attached storage (NAS) box or build a small Linux server to handle the file-hosting chores to keep your workstation from being taxed by serving files for other systems.
Depending on personal preference, you can either "publish" the files to the server before starting a render or you can actually work with the files from the server all the time. The first option means your workstation will have fast local access when interactivity is important, while the second option means you will avoid missing files and broken internal links when moving things to the server. Troubleshooting these kinds of render problems can get very tedious, and if you're not careful, you can end up spending hours rendering an entire scene only to discover afterward that a texture in the scene was either missing or not the correct version.
If you’re not currently working with your 3D files on a remote system or file server, then you have to move those files to the server and go through and fix these potential problems. After doing that, it would be a good idea to get into the habit of working with all of your scenes remotely so that the content is automatically on the remote file system, allowing you to avoid having to move the scenes over to the server when rendering tasks are performed.