E21 purchasing

Hi everyone. My name is Anil, i live in Turkey and im fan of Bmw. Ok i will ask some questions. İ want to buy e21 but i dont know what should i look for wich parts are important for me? Or where rust begins? And unseen rust? Finally sunroof or no sunroof wich one is the best selection? The last question about rust. Thanks for your answers and im sorry for the bad eng. 😊

E21 purchasing