I need to know the answer from different aspects.
1) Where can I set the maximum number of concurrent sessions in the admin tools?
2) What's the most common hardware configuration for a Terminal Server that you have seen and how many concurrent sessions can it support?
3) What's the most powerful hardware confiugration for a Terminal Server that you have seen and how many concurrent sessions can it support?
EDIT
Assuming that the user is just using Microsoft Office and maybe some admin tools.