As you know LP I have already PM´s you with the response as this seems to be a growing trend however the law is simple, that if you are receiving any direct payment for the use of the car then you require special hire and reward type insurance and, in the case of an accident or legal problem, the driver would not be insured and both the owner and the driver would be liable to prosecution
Both the renter and the owner are leaving themselves wide open as there are lots of roadside checks and if stopped and the driver does not have the necessary documents with them the car can be taken away and the driver will be prosecuted if anything is wrong with the car perhaps no MOT, or bad tyres
With more than 20 speed cameras now in this area the owners are leaving themselves wide open because without an agreement and the right insurance they will get the fines and points, unlike a rental compant that covers this in an agreement and the driver still gets the fines
I personally would not doing this knowing the traffic laws and that it is normal to call the Police for most road traffic accidents
It is correct that in Spain you insure the car not the driver so it can then be driven by anybody over 25 fully insured, ideal for frineds and family but the isue is with a car attached to the property how do you cover any motoring offences