If your son is over age 21, he cannot be included as your child in your I-526 petition because he is no longer a child under U.S. immigration law. If he is legally incompetent by reason of Down Syndrome and there is an official diagnosis in place, he cannot sign contracts or other legal documents such as offering documentation for the purposes of investing under the EB-5 program, because he does not have the legal capacity to do so.
I have a 26 year old son with Down Syndrome who is dependent on us. Can he be included in my application for EB-5? If not, how would he apply for EB-5 on his own when he does not understand what he is signing?
You have to have a guardian appointed who can legally contract. Or have the principal parent get a green card and then do a humanitarian parole with a family F2B filing, but the wait line is many years.