buyers agent but no listing agent

I have read and understand the theory of using a buyers agent because the seller pays the cost. So why would you not? However, does this theory remain when the seller does not have a listing agent? I have  a coworker that wants out of his house.  My only "need" for a buyers agent would be to walk me through the steps of closing that I am just starting to get familiar with, and make sure the sale is done properly.  But then how will she get paid? Am I taking money out of my sellers hands? Out of my own hands?