Personally I don't believe in buying a car with deposit, If i want a car i will have spent weeks ahead of time investigating what insurance or tax or even service parts would cost before hand and once i'm satisfied i make sure i have the full amount in cash, i commit to looking at the car if its not to my standards (condition both mechanically and aesthetically) I walk away, If it is i pay the owner and drive away, It saves a lot of ball ache and messing about both people come to an agreement to view the car and test drive it but both need to know there is no obligation to buy, if an appointment is made stick to it, and disclose if there is other interested parties involved, that way every one knows where they stand, especially if the new buyer has travel costs incurred coming to view the car, to come all that way at significant cost only to be told you loose the deposit is BS IMO.