Add Multiple Instances to existing code

We have a program that is a CRM and is set up for only 1 company. We would like to be able to add more than one company. We want to edit the source code to add the ability for multiple company accounts. Each company account has private access to it's own data and resources. We would need to edit the my sql database structure and code to add this feature. Basically we would like to have each company that signs up through our portal to have their own private access to the software for their own company or individual needs. Then when a new user comes to the site they will be able to fill out a brief information form and select a login and password to gain access to their own private area. I hope this makes sense. Please let me know what you think and if you can do this along with the other part of the project. Check the attached document for the information on downloading the source. Please take a look at the source and project and give me a realistic bid and time frame. We are anxious to get this completed. Also if you have any questions, please ask me. Thanks for your interest.