Modifying and consolidating the login process for two PHP based programs/sites.

Summary:
Merge the login process for two PHP based websites so that my users will only have to register and login once to use both programs. This is a freelancer type of website with a specific niche, and will have two types of users (the typical employer and freelancer).

Specific:
My site is comprised of three programs; Joomla, a PHP based freelancer script, and PHP based Questions and Answers script. The niche will be for legal services. The two types of users will be Clients (looking to ask legal questions and post legal projects) and Lawyers (who will create profiles, answer legal questions, and submit proposals to project postings). There will be NO need to work within the Joomla program, as it serves simply as a landing page.

Task 1:
1. Merge the login process for the client, so they only have to register once and login once. Once they are logged in, they have access to use of both programs ( the Q&A script and the freelancer script). Registration should take place through the Freelancer Script,

2. Implement Facebook login functionality so that Clients can login with their Facebook accounts if they choose to.

3. Create a separate login page for Attorneys. Registration should take place through the Freelancer script, and Attorney profile data should also populate/take effect in the Q&A script.

4. Limit access according to roles: The Freelancer script currently limits bidding on jobs to freelancers/attorneys. This should remain. However, the Q&A script allows questions to be answered by any registered user. This needs to be changed. Only users registered as attorneys should be allowed to answer questions in the Q&A script. In the end, only users registered as Attorneys can submit proposals and answer questions.

I've posted a similar project in the past, but my needs eventually changed. This project will definitely be needed as described, and will be awarded within the next 30 - 60 days.