Same problem here. Set up a special needs trust with help from your local office of disabilities/ SSI, or a private attourny.
Pardon me for using. Different terminology, but it sounds like you are concerned about a child with intellectual disability, who is expected to require life-long supports to be able to function in the community. It is important to use this term when applying for resources & funding. You can apply for SSI & katie beckett for him now. The school begins transition to adulthood at age 14. Call family ties for support.