I would not rent a car with a debit card, first and foremost. There are many reasons, from authorized holds on your funds in your account to damage claims automatically debiting (yes, this happens).
Otherwise, if you currently have a car (and insurance) double check your policy to ensure you are covered sufficiently for renting a car.
Age shouldn't be an issue as you are 25 now (18 - 24 are usually surcharged).