If you Orbitz or Travelocity car rentals, they will show you any additional fees in the rate details link.
A friend of mine use to rent from Dollar specifically because they'd let him do it when he was not yet 25.
I mostly rent from Budget because the price is usually best.
I advise you do not rent from some no-name car rental place. For instance, Payless Car Rental is the biggest bunch of thieves on the planet. I rented from them once in SFO, and they wanted to confirm my insurance, but couldn't. They forced me to buy insurance (cost more than the car rental) until the next morning when my insurance office opened and they could confirm. They rented me a POS with power nothing, no AC, and 300K miles on it. It shook when I took it up to 50mph.
Despite my warnings, my older sister rented from them at LAX. They wouldn't accept her out of state insurance, so I said I'd rent it. They wanted proof of insurance which I gave them. Then they said they had to charge an extra fee to rent to anyone from a local county (Ventura, LA, Orange). I'm not sure why, but they actually had a sign that said it right there on the counter.
I told them I lived in Santa Barbara county, so the guy just didn't want to rent the car to us anymore.
It's not worth the pain to rent from some no-name company. You'll regret it.
