Dear BF,
Yes, there is help out there for your son, and unfortunately it does take a bit of research to find it.
All pharmaceutical companies that manufacture MS disease-modifying therapies have patient assistance programs for uninsured patients. They will furnish the drug free of charge. Your son's neurologist should have given you literature with the drug company patient services contact info, but you can find the contact info on their website, too. These patient support services can help guide you to other resources, too.
Another resource for financial assistance is NORD (National Organization for Rare Disorders), which will also cover the cost of expensive MS drugs. Find their website for application info.
You can also contact your local chapter of the NMSS (National Multiple Sclerosis Society), the MSAA (Multiple Sclerosis Assoc of America) and MSF (Multiple Sclerosis Foundation). Search their websites for contact info. Staff will help you find resources in your area.
For doctoring, you'll need to research your county community health clinic. If your son meets the income guidelines he can receive free care. Same goes for private charity clinics, both secular and religious. I've used those myself when I was uninsured and unemployed. I even used one outside my county, so if your city/county is short on charity clinics, you can search outside your immediate area, too.
Catholic Hospitals have Care for the Poor programs. If you use a free clinic and the doc sends you to a hospital for an MRI or blood work, those hospitals with charity programs will provide those services free of charge.
Hope this helps.
Kim