Sometimes a client will buy a house with the intention of renting it our. Other times a client is going to be away for a couple years and wants to rent his house, or she has bought another house and wants to rent the old one since it hasn't sold. Do you manage that for them?
For several years we reluctantly did locate tenants for clients with homes in my neighborhood (where it was easy to keep an eye on them) and inevitably, no matter what the contract said, the tenants came to us for property management issues as well (after all, we were right here and the owners were in Europe). Finding tenants I don't mind, but property management I do, so now we refer out all of the rentals. Some agents make a lot of money on rentals, but for us, it's a matter of keeping to our niche, doing what we do well, and doing what we like.

Rentals if done properly can add to the bottom line. It depends on who`s running that side of the business.
Sharon,
There was a time when I did property management for my REO clients. It was not my favorite thing to do. These days we do not do property management, we refer it all out.
You are right in doing what you do best.