Towing using a car with a manual gearbox means that the clutch is the component most likely to suffer, although unless you know exactly what the previous owner towed and how frequently it does not necessarily mean that the car will have suffered as a result. A worn clutch may reveal itself through excessive noise, smell or a high biting point, but without these indicators it is difficult to know its condition without taking the gearbox apart. The clutch and the brakes are components that will eventually wear out and need replacing regardless, but if you have any doubts we would suggest looking for other examples for sale.