My daughter is 15. If she chooses to stay in school I will support her but if she chooses to go to work. I will charge her rent but it will not line my pockets. It will go into a savings account for when the time comes and she is ready to move out.
I do this for my 19 year old, she is working, and has a lot of disposable income, so I charge £200 a month, but she gets a lot for free, basic clothing, toiletries, food, sim, access to streaming services, air con in her room etc.. basically she only pays for her car/fuel and going out with mates..
That £200 goes directly to a savings account for her, she doesn’t know this and does challenge the amount of rent/keep she pays, but always backs down when doing any form of calculation, because she is living the high life..
I paid £200 a month back in 1990 and never got this back, it didn't bother me and didn't motivate nor demotivate me in anyway, I knew when I wanted to move out as I was growing older/girlfriends etc and did so.. When I was saving for a deposit, I did have a word about the rent and did get 6 months rent free at the end..
The fact I had food provided for all meals, and basic toiletries and underwear/socks and the basics meant I knew I had it easy and didn't complain.
My daughter has £250 a week of disposable income.. after all her bills and travel to work, that's a nice amount yet she isn't remotely thinking of her own place yet, but we are already in the position of 'cars' where the nice low mileage Ford Ka she has currently (£5.5k) she thinks is slow and already wanting to spend £15k on something much newer/faster.. So we are going through the whole 'savings' aspect (she's saved £6k) and the crazy interest rates (Her bank want 27%APR for a personal loan!) and trying to help her through that, but the reality is, she is in the wasteful phase of cars/friends/going out..
So her hidden £200pm rent or 'savings' might come in handy, I almost thought it would be better at £300.. so after 2-4 years she has £7200-£14400 saved for a deposit, I mean you can try to educate them on finances etc, but at 19 with loads of disposable income, and showing her the true cost of buying more expensive cars.
It's absolutely fine to charge your kids nothing, everyone is different and if they are financially responsible is not a given no matter how much you think you educate them and support them. It is also not a given it will motivate or de-motivate them either, that's down to the individual as well..