I agree with the above posts, consulting with a local expert might be the best way to go, or finding a community that is specific to that area. There might be a facebook group or something where you can find information.
You can buy a property in Karachi after consulting the local Real Estate Agent. In Karachi lots of good areas where you invest to buy a property like North Nazimabad Karachi, Gulistan-e-johar, and Defence Housing Authority(DHA). But I suggest you before buy a property must get all knowledge of property rate about the area.