Develop Sub Site for Client Login

I would like a subsite built that my clients can go to that log in with a custom user login (unique to each client) and then each client gets three options. First to view and pay invoices, second view progress of plan, and third to view a copy of their plan. This site content will have to be different for each client. So a back end interface will be needed so that we can additional users and upload additional content based on each client. The site can look exactly the same for each client and the type of content will be the same for all but the actual invoice amounts will very and each will have different stages of progress etc... Please let me know if this is something you can make and i look forward to reviewing your bids. our current site is [login to view URL] so i want it to look the same color wise and design wise.