@ seakings
I wish I had a definite reply to your querry. Its a very difficult question. Depends on what you plan on doing with the car.....theres a WIDE range of options to choose from each step of the way and the cumulative effect would dictate the total cost at the end.
Lets see.....if you give us what you have in mind we can be a little more specific in guiding you.....
The plus point of this car is it requires no major engine work so a BIG expense is spared, plus if the buyer is a novice to tech stuff he would be safe from the often complicated venture of an engine rebuild.
The bare minimum this bug needs is a new Battery, a brake rebuild/service (depends on what you find when the system is inspected) and fuel in the tank. Maybe a little TLC here n there.
The best route one can take is to get the body bare metalled, get all the rusted bits sorted (there wont be very many considering a 40 year old KARACHI car) and go on with a good quality paintjob.
Interior may be reupholstered in your favorite color combo.
