At 13 years old you can expect a number of problems, both through wear and tear and ageing of components. You need to be reassured at least that the oil and oil filter have been replaced every year. You need to know when the coolant, brake fluid and automatic transmission fluid were last changed. You need to inspect the car very carefully for rust, damaged door and window seals, soggy carpets, etc. Check the sidewalls of the tyres for cracking and assume they will be over age (over five years old). That's just a start. But if the car is cheap, then judge it on 'gut feel' both about the car and about the person selling it. It it's expensive, then simply walk away. An old car is an old car. Market values are currently rock bottom. No sense in paying strong money for an old car just because it has 'low mileage'.