WordPress / PHP Master Needed.

I am presently developing my company's new WordPress based website, I need somebody to come on to help me build a back-end which will allow our users to pay to publish on our news circuit. I'm open to suggestions on plug-ins but, have strict design and functionality requirements which should not be taken on by an amateur.

What Exactly I need:

Users will log-in to their individual accounts, provide basic tools (which I can develop) such as Password Retrieval, Change Personal Account Details, and the main functionality will be to submit an Article which will then generate a PayPal payment based on their particular distribution requests, this would put the "post" into a pending category submitting via email/sms to our team for approval and fulfillment.

We would like to be able to add other tools to this "dashboard" later, and would be looking to keep somebody on long term for various other exercises including social media management and general webmaster work.