It's isn't *necessary* @Melissa Man , but it depends on how comfortable you are and want to be. Insurance is for the unexpected. If you feel you are sufficiently protected with your homeowner's insurance and don't need more, then that's a fine decision to make. If you want to be more protected, you can get umbrella coverage on top of the homeowner's.
My pleasure - good luck! Where in NJ do you have your rental?