I’m a firm believer in young adults in full-time work (post-18 and not in education) paying their way. I think not charging them keep (not necessarily rent but their proportion of food and bills at least) risks spoiling them, and I have seen it happen.
Life costs money. I think young people learn more respect for money (and their parents), more responsibility, and more awareness of saving and budgeting when they have to contribute the moment they’re working full-time. Taking a contribution towards keep isn’t capitalising off them, but teaching them - and respecting yourself.
It’s also narrow-minded to be blanket against this if you’re coming at it from a relatively financially comfortable household and with your DC’s other parent sharing the costs.
By the time their kids reach young adulthood, many parents are on their own (or as good as) income-wise - widowed, single with child maintenance having stopped (or never there in the first place), one parent unable to work due to ill health or disability, etc. Parents still fully funding their adult DC in more challenging (or even average) financial circumstances, while often watching their kids enjoy more disposable income than they have themselves, are being martyrs and spoiling their children. What does the adult child learn from this?
I have raised adult DC solo since toddlerhood with inconsistent and for many years no financial support from Dad. I have a mortgage in my name only to pay off eventually (it’s interest-only and while I do save enough, I’d like to clear it before I’m ancient!). I’m helping fund DC through uni, so saving less than I’d like towards the mortgage and my pension at the moment. DC is monumentally grateful for the parenting and financial support I’ve given, and fully expects and wants to contribute once working full-time. DC is responsible, aware of different people’s circumstances, sensible, has put together a budget in a spreadsheet for uni, has started a pension - DC has learned financial responsibility early.
I won’t profiteer off DC. But they will pay their share of bills and food - anything they consume (not “rent”), and I will put this towards my own future security, which I have compromised somewhat to give them the best start - and they will still be in a position to save a lot. They know they can live at home as long as they want or need.
A friend did the same with her DC, charging them a modest amount per month, and they resented paying a few hundred £ a month, so moved in with their dad where they pay nothing. They are constantly buying expensive branded clothes and other items, holidaying and going out drinking, instead of saving for a house. They are earning nearly £30,000 and frequently report being broke.
Even if I was loaded, I’d still charge adult DC their share of bills (and as some have said, save this to help them out down the line). They need to learn that life costs money and not slip into an attitude of entitlement. Yes, it’s their home. But it’s also yours, and it costs money!
If you’re not going to charge adult DCs anything, at least have an agreement that they’ll save X% of their take-home pay while living at home. Otherwise your “generosity” might instead be facilitating them to spend frivolously and fritter, while denying them the opportunity - the necessity - to learn to budget and save.