The most common areas are the front wings which are easily replaced, rear wheel arches and on saloons the spare wheel well. Doors can suffer from rot in the lower regions and spare doors are becoming scarce. Obviously if one finds a badly rusted car, especially in the floor pan, one should seriously consider the cost of repair. Bonnets and boot lids are generally rot free. Interiors, replacement material is scarce but the average car does not usually suffer from poor interiors as the original is very durable.
Mechanical problems are usually down to lack of servicing.
Engines will last 150,000 miles before major work is required, especially if the oil has been changed regularly along with the oil filter. The early B16 engine is somewhat rare and the spares for it are becoming very difficult to obtain. The later B18 and B20's do not have this problem. The transmission is a very robust affair, gearboxes are almost unbreakable, any judder is probably worn engine and gearbox rubbers. Service the car at the recommended intervals ie change the engine oil at 3,000 miles and the filter at 6,000 miles.