Social networking app maker

I need an Android, iPhone app. I would like it designed and built. My project is about making mobile app in which user can post his/her plan socially. It will send that info to his/her selected friends. His/her friends will get notification about plan and if they want to join they will join there will be two option like yes or no. These was basic idea. I'm looking for expert to build and design these app for me. I want only professionals.