Also, is it possible to rent a car in Seville and drop it off in Algarve?
I'm traveling with a bunch of friends to Spain-Portugal, and we are planning to drive down the coast.
What documentation is required to drive in Spain?
You must be 18 year old:
To drive in Spain you must be aged 18 or over. To rent a vehicle you must be 21 or over. Many companies also require you to have held your driver’s license for a minimum of one or two years. Remember that you will also require a credit card to rent a vehicle.
A valid driver’s license:
If you are the citizen of an EU member state, Switzerland, Norway, Iceland or Liechtenstein: you only require your valid driver’s license. If you are from another country you will require an International Driver’s License.
Given that conditions may vary, we suggest that you contact the Spanish Embassy or Consulate to verify these requirements before you start your trip.
If "Algarve" is Faro Algarve, Portugal, then yes, you can drop it off there. Kayak and other aggregators and most car rental companies will let you search and find out if a particular drop-off point is possible.