What you likely want is a small to medium NAS, preferably one with RAID 2 or better. Most often NAS systems are connected via 1 GBit Ethernet, making them substantially slower than internal harddisks or very fast (USB 3/Thunderbolt) external disks. You will notice this when loading or saving larger files. If you invets a bit more into the NAS you can get 10 GBit, but this requires matching network adapter sin your computers.
Personaly i would go for a 4-5 bay mid range NAS from Synology or QNAP with 1GBit Ethernet. It might affect the time it needs until a rendering starts, but the rendertime itself will not be negatively influenced.
A NAS also makes it easy to do backups by attaching a backup disk to it and setting up an automatic backup to it.