Financial assessment for adult respite

Hi, My autistic adult child will be having a financial assessment, They live with me, non verbal and I am the appointee for benefits & money. he/she needs all care and health needs met by us. he/she has started some overnight respite. What contributions would the council expect them to pay to live at home with me? this will be towards foods & bills. we do spend a lot of money to help him & have additional expenses within the home eg extra laundry & breakages. My mind has gone blank with what I should consider as extra expenses when he has his assessment. Any advise would be useful. Thank you