Develop a revamped facebook/whatsapp mobile application - open to bidding

Hi Elangora, It is nice to know you. I need to have a mobile application whose function is a combination of facebook and whatsapp. It will reinvent what facebook and whatsapp have into a single application. The chat lines and fb postings will be treated similarly. The new application will have additional and/or enhanced features. The server side will be facebook like where all chat lines and posting will be kept in the server. Tell me what you think and how much roughly do you estimate to build this kind of requirement. Regards, Isa Tahir