Messaging System with allowed Attachment of Files

I am looking for a programmer to add a login page to my current website that, after logging in allows users to communicate to each other much like how GAF has their messaging system. Should be able to attach files. Should allow messages to look 'threaded' like a conversation. So, basically what I need is.. when a user submits the order form on my page, it stores the data and automatically generates an order number. It then automatically generates a user name/password for the customer. Where the customer can log in and interact with a designer using a messaging system. 1) Allow an administrator backend so that I can view all accounts. 2) Incorporate a Simple Paypal payment where a user can click "Payment 1" and it will request a set amount of payment from that person. and "Payment 2" which is also another set amount from that person. Please bid and tell me an exact date/time/how long it will take you to finish this product. I need punctual as well as very neat programmers with great communication. I am not looking to spend more than 50 dollars on this. If you bid lower chances are i'll probably choose you if you have wonderful feedback! I make very prompt payment. Thanks.