Thanks for reaching out. The timing depends on you. Luckily, you don't need to contact support to prepare the hub for the new owners.
Please follow these steps:
- Go to Settings and select Z-Wave Details, then reset the radio by typing the word "reset" in the "Reset Z-Wave Radio" box.
- Go to Settings and select Zigbee Details then reset the radio by typing the word "reset" in the "Reset Zigbee Radio" box.
- Perform a Soft Reset without restoring a backup by following instructions in this document
- Log into my.hubitat.com and click Deregister Hub (see this post for more details).
Hope this helps