@Grapewrath
Some people live in dreamland. DD is an adult, not a dependant and £400 pcm for all rent and bills plus food is more than reasonable. She’d pay far more elsewhere and OP shouldn’t have to subsidise her adult child if she can’t afford to!
Agree.
My ds gets pip. It comes to me through this choice because he cannot manage budgeting.
I pay for his swimming, phone, clothes, nice toiletries and days out etc
I also work less hours because I need to be there to care for him and if you work you cannot get carers allowance.
When he starts work this year and gets a job we've discussed what will happen as he'll have to contribute to rent, food and bills.
So he either gets his pip and wages and pays for everything himself and contributes towards the bills at £400/500 a month or I continue to get his pip, pay for those things and he contributes £300ish a month.
People just seem to get that raising a disabled child is easier because of tax credits. When they become an adult you lose that. He can claim wtc but not me on a low wage who will remain limited because of caring for him.
And comparing living at home to elsewhere doesn't really work because he couldn't live independently. But if he was to go down that route it would be same rent as I pay here on HA 2 bed for a studio/1 bed. Another set of bills and council tax plus paying for people to come and help him/ company to deliver meals/ cleaner etc.
I'm a much cheaper option 
