The decision to be made is whether what is pictured is specific or systematic. Being from Florida where rust free 30 year old MBs are the norm rather than the exception, I wouldn't touch that car unless the example is due to previous poorly done body work.
If on the other hand the rust is systematic the car is history. Its also over priced at 4000. Those cars have NO clasic value and probably never will. In my area a coupe won't even get the money a sedan will when they are that old. Its just transportation by now and harder to get into with only two doors.
Bosch Master, ASE Master, L1
33 years MB technician