Question: questions to ask when buying a used porsche 911?
Answer: Which Generation? From the very beginning, even until present day, the Porsche 911 was classified into specific "eras" that retained specific features, styling and upgrades to the overall design, performance, etc. ... 
Air-cooled or Water-cooled? ... 
What Should I Look Out For? ... 
Which One Suits Me? ... 
Coupe, Convertible or Targa?