Contributor restriction

I want to let one person to be able to make posts in the blog, however, I dont want them being able to access anything else. Ideally I would like them to have a media section for uploading their images that does not get included in the main media area as well. The idea being that they can log in, upload an image to their area and add text to a blog post that is then made public. Any thoughts on the best plugin for this.