1983 Porsche 924 4 cyl Two Wheel Drive Manual 80,000 miles

I am more than willing to make a donation if you can correctly help me with my question... I have not yet purchased this car but and ready to do so... It is beeing sold very cheep due to the passenger side door not closing and the Drivers side door not opening... The guy at the store said that it is a pretty common thing wiht the 80- 83' Porsche 924's... Is that true and how difficult or expensive will it be to fix???