you can contact any lawyer in Mumbai . be very careful before signing any agreement with the builder . to protect your interests see to it that builder undertakes to complete project within specific period of time and furnishes bank guarantee

Is the Society having Conveyance in its favour?? If not first v should send Notice to Builder/developer and plot owners to get Conveyance.

If they do not cooperate, need to apply for Deemed Conveyance.

Once Society has Conveyance, u can proceed for Redevelopment.

V have worked for many societies in Mumbai. U can come to our office after taking prior Appointment.

Hope the society has completed conveyance procedure. Explore all options/negotiations before signing a redevelopment deal with any builder. If needed I'm here to help.