Also, if you have an American Express card, sign up for their rental insurance, its free!
Some Visa cards also offer it. I have one with capitalone and I have the service for free, helps save a lot of money.
And yeah renting cars under 25yo sucks, did it many times and payed a lot of cash for it. I know some people like pre-med students get a card that exempts then from paying the extra cost.