need help for devloping social networking app.

Sounds like you need to hire someone who knows how to code that can put your "idea" into app form.

 

You are looking for someone to create your idea.. for free? I don't really see what the issue is, you don't know where to start.
Have u tried reading through some books of how you have to start apps, what architecture through your code etc.
And i'm not a big fan of Three20 code, it has tends to.. Crash..
That's why I allways code from scratch. So i think you need to hire an consultant of how to build your project, and actually, the hardest thing is writing it all down from scratch. Like when you design games, you make an GDD. which pins you down to follow one road after you finally wrote every single thing down, or you keep adding features and features, which ends up in never finishing the app at all

 

I just think you don't know what your app will do exactly, if you have figured out your entire flow.
Because, a login based appication. What I do, is check on the appdelegate, check if there is an user saved or not, and pop a modal view controller, which won't be able to go away unless a user logs in, which works fine.
You should maybe break your app down in smaller bits, or i'm 80% sure it will end up on the non-finished apps pile.
Signup -> textfields, -> create user instance, send to server. Maybe keep user instance shared for use somewhere else etc.
These arent things done without any knowledge very fast.
I think these are your option:
- Face that you have to deal with several months of learning curve -> expensive
- Hire a developer to co/develop it with you -> expensive

 

Would you be better going all Web. Maybe looking at one the HTML5 based web app frameworks designed to work with touch platforms. Any reason your jumping straight to Native app that will be platform dependent?

I guess you really need to work out what's the product, who are the customers, what is the experience?
Start sketching that out working out the flow as others have said above.
Work out what is the hook that'll keep your customers happy. Then you might have a snowballs chances of working out how to code it.