Originally Posted by wahooflyer
Avis and Hertz do not rent to under 25s, period, unless you work for a company that has a special contract with either agency.
No. Both Avis and Hertz do rent cars to under 25s, just not in all of the countries they operate in (randomly checked Greece for Hertz and Romania for Avis and they do it).
Originally Posted by wahooflyer
if anyone has experience renting cars in Europe under the age of 25, feel free to enlighten us! Most agencies there have a minimum age of at least 23).
As I said above, this is simply not true. Depends on the country, the size of the car you want to rent and the individual rental company.
Sixt's low-cost operation,
www.sixti.de, is quite cheap and has a min age requirement of just 18. They are far from omnipresent, though.
I usually travel either alone or with one other person. First class train in most of Europe (the UK is an exception) is cheaper and more comfortable than renting a car, paying for petrol, getting lost etc.