Landlords of Reddit, question about adding? Roomates

Or anyone educated on this topic I guess... Okay so here's the situation... My friend from my home state is wanting to relocate to the state that I currently am in. My roommate and I have both decided we would be okay with her living with us till the remainder of our lease (which will have 6 months left on it when she moves out here), before all three of us get out own, bigger, apartment. What should we do? Just have her stay with us, don't tell anyone, and have her pay my roommate and I rent? Or could we potentially get in trouble? Is there a way of legally doing this with our apartment complex or would they be okay with her just paying us rent? The two of us can easily afford rent without her son it's not like we would be relying on her payments. Thanks !