Is liability insurance mandatory when renting?

Whether it's required depends on your lease agreement and your state's laws, but most rental contracts do require it! Even when it's not mandatory by law, landlords usually make it a condition of the lease to protect themselves from damage you might cause. It's definitely worth having because it's cheap and saves you from heavy legal trouble if something goes wrong with the property.

The best thing is to check your specific lease agreement and then your country's rental laws, because the answer varies quite a bit. In some cases it's mandatory by law, in others only the landlord requires it in the contract, and there are places where it's completely optional - so you can't really generalize as if it were always the same.