Upvote:5
As a rule, there are no special requirements, all you need is a valid driver's license and a credit card. (Some companies will also accept debit cards.). If you're under 25, many companies will charge an extra fee and limit the cars you can get (no sports car for you), but they don't require anything else.
Insurance for the car and third parties is covered by your rental agreement, with better insurance options often quite expensive (getting this separately can be much cheaper, and some credit cards include some level of insurance). Your personal medical insurance is up to you, not the rental company.