A basement bedroom needs a code-compliant egress window: a way out in a fire, and a way in for a firefighter. It is also what determines whether a finished basement room can legally be called a bedroom when you sell.
The work involves cutting the foundation opening, setting the window and well, and finishing the surround. It is dusty, heavy work and it needs doing correctly.
If you are finishing a basement, this is worth handling before the finish work rather than after.