Can you join multiple Realms without paying?
If you haven’t subscribed to Minecraft Realms, i.e. you haven’t bought anything, are you only limited to one Realm you can join or you can join/be invited to multiple Realms?
You can join as many Realms as you want! You only need to pay if you want to OWN a Realm. This can be confirmed with a screenshot from the How do I join a Realm FAQ:
Also, with a quick Google search I was able to find this picture that also confirms that is possible to join multiple Realms: