Your question really has two parts... finding a car rental company that will allow you to
have a 20 year old as an additional driver in New York and finding a company that will allow you to do a one way rental to Miami.
We can start by narrowing down the companies that will allow a 20 year old additional driver and what the rental car underage fees for an additional driver are in New York (auto rental links open in new windows) (note: fees given were applicable on the date of this answer and may have changed - please double check any fees with the provider of your choice)
states that all additional drivers must meet all the rental qualifications of the pickup location, be present at the rental counter with the renter, present a valid driver's license and must sign the rental agreement.
Alamo Rental Car Underage Fees for an Additional Driver in New York:
The minimum age for NY is 18 years of age.
In addition to the daily rate there will also be a
$3 a day additional driver fee
and a $70.00 per day additional charge for underage drivers aged 18-20Dollar.com
any additional driver must be able to meet the age requirements, have a valid drivers license and must meet other rental car requirements, which may vary by location. There are additional driver fees, but not available without knowing a specific location. I was unable to find information about the rental car underage fees for an additional driver in New York either... you would have to contact the specific location you wished to rent from to find out what the fee may be.
The age requirement for extra drivers is unclear on
It states that all additional drivers must meet the age requirement for the location (which is 18 or over for New York), but when I tried to check a rate and the fees for under 25, the website stated that those reservations could not be booked online and that you must call 1-800-261-7331 in order to check policy info for additional drivers under 25 for the individual location that you wish to rent from.
According to Nationalcar.com:
National Rental Car Underage Fees for an Additional Driver in New York:
The extra driver can be added for an additional $70.00 per day fee.
They would need to have a major credit card in his or her name, and they would need to be approved through the Loss Damage Control department. You would have to contact the particular location that you wished to rent from (before the rental dates) and the primary driver and the additional driver would have to go to the location a couple of days prior to renting.
You will only be allowed to rent up to a mid sized car.>Thrifty.com
all drivers must meet location age requirements.
For Thrifty rentals in the state of New York, the minimum age is 18.
Thrifty Rental Car Underage Fees for an Additional Driver in New York:
Underage additional drivers age 18 through 20 will be charged a under age driver fee of $72.99 per day, Additional drivers are also charged $3.00 extra per day. All additional drivers must present a credit card in their own name at the rental counter.
-- All authorized extra drivers must be 25 or older.
That was the easy part... the more difficult part will perhaps be finding a company that will allow you to do a one way rental to Miami. There are no guarantees on availability for one way rentals.. you will have to compare several companies for the dates and times, and pickup and drop off location that you're looking for, in order to determine availability and rates.. Just remember to add in the extra underage fees and additional driver fees.. these won't show on a rate quote that you get online.