This is not what happens to me, just something I think about and wonder if it ever happens in academia.
Suppose that there is a funded project which is planned to have 3 people working in it for a certain amount of time. At one point of time, a new member, who can be a PhD student or a post-doc, is added into a project. I can think of few reasons to add a new member to a project: to help her gain some experience, or just because there is some additional work to be done but is not initially planned.
However, as it is initially planned that there are only 3 people working in it, which means the funding only covers salary paid to 3, does it mean a new member has to work without being paid?