Do you need car insurance if you do not own a vehicle but drive another persons vehicle?

You dont NEED insurance in that case you are covered under what is called 'permissive use' on the owners policy, permissive use does not mean you drive the vehicle frequently (not more than 10-20% of the time) but you have the permission to drive the vehicle from the owner/policyholder.

You can get "Non Owner" insurance policies in some states that dont require you to actually own a vehicle, this is in SOME states and your driving record needs to be pretty nice looking but it is available.