The trend was coined by the retarded used car salesman that we have on every nook and cranny in Pakistan. - The jenyan pent term is used like a hired courtisan and also used to lie and cheat too. IMO a scratched up, rusted, worn out POS is scrap metal. An old car should be maintained to keep the cancer (rust) out of the question completely.
A good inspection can give you your answers for any car e.g. If the floorboards or door sills have been replaced and you see open seams, no sealant, no wax coat - leave it - its 100% guaranteed that it will rust out. similarly if its still in "JENYAN PENT" - leave it unless you want to repair it correctly.
a good body refinish job is worth all the money spent, for me it does not make sense to paint over moldings, nuts, bolts, door strikers etc with cheap expired paint just to "paint" the car cheaply - its equal to buying a can of berger enamel paint and brush it on.
Most (as in all) used car salesman in Karachi hated me because I would point out repair and shoddy workmanship that they were peddling as "zabardast". Most deals never went through as the price of the car and expense to get it back to a standard I like would not make sense...
Inspect the car thoroughly and look out for rust in the most odd places - like wiper trays in a khyber or mehran, rusted door edges, badly aligned panels, cracked seam sealer, hacked up wiring. Judge your opinion on this.
The engine can be replaced
the wiring can be rebuilt/replaced
the undercarriage can be replaced/rebuilt
the body bolt on panels can be replaced
the UNIBODY cannot be replaced or rebuilt if big pieces are rusted or buckled, smaller jobs can be pulled out.
These low life, gutter scum used car salesman think that they are oversmart - and try to fool the customer at all given chances. I have experienced a dealer say that an automatic corolla not shifting at all was a normal wear problem and a "tuning" of Rs 200/- would fix it. I told him that if the autobox is a governor type - here is Rs 200/- get me a new governor or if its an electronic type - get me a new ECU or solenoids with the same Rs 200/-
Similarly the ton of GDI galants that bit the dust - most were bhai plug shart hain buss zyada kaam nahin hai. :). baaki gaari tight piece hai - paint jenyan hai, what good was the factory paint when the engine, HVAC, gauges etc were screwed up.