I can't believe nobody mentioned mileage. Engines have a life expectancy of 200,000 miles. Maybe 20% make it beyond that with good maintenance.
Parts on an engine have a different life expectancy. A timing belt for instance has a 70,000 mile life expectancy. Is the engine an interference engine? What's that? It's an engine that is designed for efficiency and the valves drop down into the piston space while the piston is down. The problem is when your timing belt or chain breaks, the piston smacks the valves and the engine is ruined.
They are good engines just as long as the timing belt/chain is kept up.
So has maintenance been done on that used vehicle? Has that timing belt been changed? Most Honda's and many other little cars fall in this category. You might think you are getting a good deal with that 80,000 mile car. But if you have to spend $3000-4000 getting a new engine, it's not such a good deal.
Interference engines can be googled and you can find out if that car has one. It's no biggie if you KNOW the timing belt has been kept up.
Another thing all should do is have a mechanic check the car out. Does the engine have good compression? A compression check is like taking a blood test. It tells all kinds of stories on the engines condition. Are the cylinders and piston rings good? Is one cylinder leaking from a bad head gasket? A head gasket will most likely be changed once in the life of the vehicle. What condition is it in? A compression check by a mechanic will give you insight.
Anytime I buy a used vehicle, I search for one with less than 120,000 miles. The lower the better. Otherwise you are buying a money pit.
Don't get me wrong, some engines and transmissions can go 400,000 miles with proper maintenance and driving habits. Those vehicles are rare and you have to consider 200,000 as a wore out engine to protect your own interest.
Most people on Craigslist sell wore out vehicles. That's the main reason they sell them. Get rid of them before the problems start. There are few good deals, but you have to shop and be careful.
Also, always check the blue book value. It's an invaluable tool. Pay at or below that price. You can go to www.kbb.com
and find the going price on any post 1990 vehicle. Some sellers try to recoop what they paid for a major repair or such. Sorry, that's just normal up keep.