Web Design for new internet idea

I am looking for a freelance webdesigner to build me a website that I can use for a new idea that I have. The website must have the following:
1. Ability for users to enter information (email address, address details etc etc) and this to be stored on a database somewhere.
2. I think I would need some kind of ralational databse to be integrated on the back end somewhere
3. The ability for users to post items (documents etc) on the web site and for this to be secure (can be viewed but not downloaded)
4. Ability for users to make secure transactions over the website
5. Ability for the administrator of the website (i.e me) to make minor changes to the web site (text etc nothing major)

Thanks