While it may depend on the exact specification of the vehicle, a Nissan Leaf with eight bars remaining on its indicator suggests it has lost around 30% of its capacity. If this car has the 30kWh battery, this means the maximum range you can expect in perfect conditions would be less than 100 miles, and if it has the 24kWh battery this figure would be less than 80 miles. Whether it is a reasonable buy depends if the price reflects the battery health and its limited range is suitable for your needs.