Client Backend portal reference

I am developing an e commerce website for a client. The website currently sells online direct to consumer.

With the redesign of the website, the customer is launching their product as wholesale to retailers. They would like a wholesale customer login that would access backend information. This information would be:

• flyer info downloads
• image downloads
• wholesale pricing

Is there a plug-in that you would recommend that would give backend, hidden pages for those with login capabilities? or, what would be your best suggestion to accomplish this?