Posted: Mon Feb 8, 2021 1:33am
A good gestor will provide you with a sale and purchase contract in Spanish & English. You and your private seller complete it and sign it.
The contract holds the seller responsible for any undiscovered debt on the car (from prior to the date of contract) .... outstanding finance, parking fines, etc. Any debts stay with the car, so a signed contract gives you a chance of legal remedy if anything big comes up.
You need a gestor to process the "change of ownership". This incurs a tax, and the gestor needs to get paid as well.
The change of ownership documentation can take a few weeks to arrive by post (possibly longer given the current Covid problems), so you will need a "justification" document to show to any interested police officer - to explain why you are driving a car that (according to his computer) belongs to someone else.