Their arrangement made sense for them, and he wasn’t spending her money.

There are several factors to consider when asking, «Is it okay for parents to charge their kids rent?» Those factors include, but are not limited to, the child’s age, the family’s financial stability, the child’s income, and the amount of time the child has lived rent-free as an adult. I think we can all agree that it’s unconscionable to charge an actual child for rent, that is to say, you will evict a kid 17 or younger for not earning their keep. That being said, there are families in such dire financial situations that they need their teenage children to work extensively to keep the lights on and food on the table. That’s not pretty, but it’s a reality for many families. 

It’s also important to consider how much rent is being charged and what is being done with that money. If a parent is charging their child far below market rate (a couple of hundred dollars a month to live in an NYC apartment, for instance), that’s less morally dubious than charging them exactly what it would cost to live with roommates or by themselves. Then again, sometimes parents charge more rent because their child has been living off them for too long and they’re trying to get them out, which can have varying degrees of success.