What I really need is a good international network of car rental stations, such that I would only have too pay for transits between places. My main problem are

What I really need is a good international network of car rental stations, such that I would only have too pay for transits between places. My main problem are holidays: renting a car for two or three weeks still seems too expensive (~1000€). I've never owned a car in my life, but my girl-friend loves driving and the discussions everytime we plan holidays are a huge pita. Likewise in the city a car sharing service that worked like that would be great. We need the car to visit our son's grandparents, and paying by the hour would easily come to 20 to 30€ per visit, while the car is mostly just sitting there waiting. Meanwhile I can only wait for autonomous cabs, I suppose :-(