Translation:They rent out their parents' apartment.
In English (or at least American English) rent can mean either side of the transaction. I rent you my car; you rent my car. So "rent" should be accepted as a correct translation in addition to "rents out" or "lets."
How do we differentiate between "rent" and "rent out" in Hebrew? The definition of "משכיר" is simply "rent", without explaining on which side of the contract one is on.
One of the things which threw me on this sentence is the idea that the offspring are renting out their parents' apartment. I can't believe it would be legal to rent out something that doesn't belong to you. So, I thought it must mean "they are renting their parents' apartment".
I put "They lease their parent's apartment" and it was marked wrong because of the apostrophe.