Most policies will cover you if you rent a car for pleasure or while your car is being repaired.  If you are renting your car for business use, there is no coverage. 

You must carry physical damage coverage which is comprehensive and collision.  If you do not have this coverage you would not be covered while renting a car.

Again, if you are not sure your policy extends coverage to your rental car talk to your agent.  Your agent can review the policy with you and let you know if the company you insure with extends coverage while renting a car.  

So, if you don’t have physical damage coverage on your policy you will have to buy the car rental’s insurance for comprehensive and collision coverage.