Find script to create a content writer agency or marketplace website

Find me the best application/script preferably in PHP and Mysql that can be used to create a website to run a content writer agency or marketplace like iwriter.com, textbroker.com, contentfly.com. The application/script can be opensource or paid. I am not looking for a monthly subscription platform. I am looking for script to create a content writer agency or marketplace website. Questions, suggestions and comments are welcomed.