Hi. They don’t need to set up a new system.
You can choose whether to provide a controller - an Amazon Fire tablet is a cheap way of doing that. Or you can tell them how to download the Sonos app and connect to your system. Do not give them your Sonos account password! Without that, they cannot get at most of your settings, but can still play music.
I would take out a separate music service subscription for the system. I don’t think they will be able to add their own accounts without your Sonos password (I think - you had better check that).
If you provide a controller, reset it and then reconnect to your system before any gueats use it (to lock out access to settings).