Are property managers necessarily seperate from investors?

[Ceril S.]

I'm a newbie so.., forgive me if this is a silly question. 

I feel like there is a lot of talk about being your own property manager and a lot of talk about property managers as seperate entities, but are there investors who also handle property management for other investors?

The reason I'm asking is because we are planning on taking the slow route of buy and holding properties and we wondered how it would be to offer our services as property managers for other owners along the way. Is it done? Or do people recommend against this.