my two cents on the topic, buy a vehicle from rawalpindi, get it restored here as its easier and you have trustworthy sources. Once its done, drive it to karachi, you shall love it. An auction Fj40 goes for something like 80k ish(or so someone qouted), fix her up from the experienced lot but under proper supervision of someone you know. Then take it.
If you plan to buy a heap of crap and restore it in time with monthly salary, bad bad idea. IF you want done right, get it done once, especially when you have to use it in a city where you don't have back up.
Just my two cents