Always avoid the ones without a fully documented maintenance/service history.How do you know how good is a car on eBay ?
and even in a shop how do you know a second car hasn't been fixed up only to last until you bring the car back home ?
Car prices around here are through the roof so i'm keen on buying second hand (still pricier than a new car in Europe or US, except when more than a couple of years old, but the little experience I have doesn't inspire me much confidence.)
