Put on your plan in front of members in association meeting. Make a list of advantages for them and explain your view. Let them discuss and decide later.
Atul, are you planning to open a clinic or big hospital? A hospital would require more space and there are many issues related to it as Nikhil said. May be they would agree if it is a clinic meant only for residents of that gated community.
I do not think the residents or the apartment owners will allow to open a hospital in a residential complex because will will hamper the owners in many ways like large number of people visiting the hospital, people standing outside the hospital and causing nuisance and ambulances making urgent visits.