More than ten per cent of the used cars offered for sale in Australia last year still had money owing on them, exposing buyers to the risk that the previous owner's finance company could take possession of the car.According to automotive bureau CarHistory, 12.8 per cent of the cars put on the market last year had an encumbrance.CarHistory said the average cost of used car was around A$14,000 but consumers spent about half a day researching their purchase.Encumbrance was not the only significant problem CarHistory found. Nine per cent of used cars offered for sale had previously been written off.Other problems included undisclosed flood damage, re-birthing and odometer windbacksIn all, 22 per cent of cars received a negative report. Only 32 per cent knew that they could do a vehicle history check before buying.Only 28 per cent of buyers did a mechanical check before buying.