Found this out tonight and thought it well worth sharing (but assume many may already know).
You can easily set up a share folder/drive on one Mac on your network for the Macs on your home (or work) network to back up to.
In the Sharing Pane of system preferences under “File sharing”
Click the plus to add a shared folder.
Right clicking on that shared folder brings up a contextual menu with “Advanced options”
Choose Time machine backup destination as an option.
This will make one of the old MacPros I’m about to get my hands on much more useful as it will become shared storage and a Time Machine backup location for the other Macs in the house.