Future of societies vs single person owned projects

Dear gurus what is legal details of societies (like multi) and single person owned projects (like faisal town or bahria)?

These allotment letters not contains any such details. These are on lease or what ? If lease then how many years ? 99 ? If lease period passes then what will be future.

Legal status of these societies has week point over cda sector plot or same. If there is any risk in such private societies then what is that.

Gurus are requested to give details please.