Web site development

I need a web site developing. I cannot discuss the idea in detail, until a confidentiality agreement has been signed. The needs of the web site are:

1. Allow registered companies to publish adverts for pieces of work (not traditional job)
2. Allow applicants to apply 
3. Allow applicant to raise time-sheets
4. Allow agency to review the time-sheets
5. Allow agency to raise invoice to company and applicant. Payments will NOT be made by the system. This will be catered for outside the system. 
6. This is an web system, with 3 user groups employers, contractor and agency. 
6. Email alerts are required at each stage of the workflow
7. Text message alerts are required at predefined stages
8. The service needs to be registered on google, so we must be able to add and change keywords 
9. Assistance with transferring the final website to the hosting provided may be needed

The solution should ideally be build in WordPress (loads of free marketing widgets for SEO etc) but i'm open to suggestions, looking for a free CMS system to utilise.
 
Full designs and static html and css can to be provided.

A non disclosure agreement would need to be signed before any further information about the business and model can be discussed. 

A quick turn around is required.