Remote desktop into multiple different workstations sharing a single DSL line

I have been asked to help setup a remote desktop solution for a small business that has about 10 workstations. All 10 workstations are sharing a single verizon dsl line with (presumably) a low-end westell DSL modem. They do not currently have a static IP.

Each person would like the ability to remote desktop into their office machine from home, though in all likelihood there will not usually be 1-2 people doing this at any time.

What are the basic obstacles I will have to deal with? I presume not having a static ip is one problem that needs to be solved, but even with a single static IP, how will the remote connection finds it way to the proper machine? Is there some routing software that can be employed here, or another method?

Links or suggestions much appreciated. I assume this problem has likely been faced by many folks before...

Use an external dynamic DNS service to associate your IP with a DNS name.

Then, you can port-forward different external ports to the same RDP port on different internal systems. This is not routing, this is just one of the many ways you can use the features of NAT.

The desktops, of course, will need to be on, and have static internal IP addresses, or else the port-forwarding won't work.