Custom URLs/Subdomains and Hyperlinks for a Single Installation?

I’m running WP Multisite 3.3. I’m starting a new business and would like to have a single new WP site for it.

I will have multiple salespeople working with me and would like to be able to assign them each their own unique subdomain so that they can each provide their own unique URL to prospects/clients. E.g., joe.[domain].com and roberta.[domain].com would appear in the browser on all pages that someone might visit, because that’s the address that Joe and Roberta each separately gave out, yet the same pages/posts from a single underlying site is what people would see.

Further, we’ll be doing actual transactions through a partner company’s existing website where exactly the above is the case so that each associate gets all their customers properly attributed to them for commissions. (The other company has had everything custom-developed on a large scale. Not WP. No help to us in doing our own site.) So it would be great if, within our WP site, we could create hyperlinks like joe.[other-domain].com and roberta.[other-domain].com simply by pulling the joe or roberta subdomain name automatically to attach it to [other-domain].com to dynamically create all the appropriate hyperlinks within our WP pages/posts to take people to the external site.

Any ideas?