Android Chatting Application

I need a Android Chatting App. - User can register account and fill their interest in signup form - They can chat in group or by category(I will give you a category name) - I think I also need a server for running a chat Application?(means they'ill register a account so their info send to my chat server?) I am new to android and freelance so please also setup my chat server.. (I really don't know anything about this..) Please note: I want to help other peoples(this app is only for who is suffering from social-anxiety) so I decided to spend money on this and help them, my budget is low..