I'm about to buy a 2009 charger with 121k miles on it is
that a good idea and how much longer will it last before I
have to replace the motor & transmission.?
hard to say. Depends on how it was taken care of. replace the oil and trans fluids on a regular basis to increase your chances of them lasting till you have to replace or repair.
Search Dodge Charger Questions
Dodge Charger Experts