Medical coverage in the US is a complicated mix.
Different programs are available in different states.
The eligibility for help is different depending on where you are. I would look into the local AIDS service organization, which will have case managers who should be familiar with Ryan White and other programs, talk to the case manager or social worker at the clinic or practice where he gets care, and talk to the state medicaid agency to see if he is eligible for medicaid. If he is a member of a church that may be another resource. Good luck, and look into every option, read carefully, and follow through. Often it requires a lot of attention to detail to make the options work.