Android Messenger App (whatsapp like) for Rural Government Doctors Around 3500 members in karnataka

i wanted android app developers for messenger app it should be whatsapp like features and having customized profile for doctors. I will give data of all the cities in Karnataka, blocks districts, villages. medical colleges, courses. and some information after accepting the project. it is my own interest no one is funding. it is not business app it is social networking app. i need the estimation of hosting this app when at a time 300 to 400 login occurs. the message should be deleted after 1 month automatically to free up disk space in server. you can use opensource code to reduce time for development . i also need the website interference to see the daily activities . and to monitor the members in my website.