Buy a 1968 classic mustang or a newer car?
No matter which one you get, you should research common issues that might require replacement to compare if you can afford to fix the car if it breaks. E.g. Brakes, rotors, bulbs, headlights. Most of these things seem like they would be simple to fix but depending on the age/make of the vehicle, the costs can be ridiculously high.
Are you looking for a fun ride on the weekends or something to drive rain/snow/sun every day?
Classics are wonderful but they're also not meant to be an every day car. It would be a travesty to use such a difficult to find vehicle every day, especially if it's in pristine shape, because it severely depreciates the car's life and condition.