Car rental companies like Hertz, Avis, and Enterprise impose additional fees on renters under 25 years old, which can significantly increase the overall rental cost. Enterprise allows rentals starting at age 21, with young renters paying an extra fee of approximately $25 per day. In Michigan and New York, the minimum rental age is lowered to 18, but renters in these states face even steeper fees. For instance, Michigan renters aged 18-20 incur an additional charge of $36.50 per day, while in New York, the fee can reach $84 daily for the same age group. Hertz's young renter fee is also $25 per day, considered lower than the industry average. Avis similarly charges young renters, with fees of $41 per day for those aged 18-20 in Michigan and $35 for those aged 21-24. These varying fees underscore the importance of checking state-specific regulations before renting a vehicle, as they can substantially impact rental costs.