Hi, I can offer my own perspective as an autistic adult living alone.
Depending on what kind of city/county you live in there might not be any supportive housing options for autistic adults. It all depends on your local government and any nonprofits in the area. In Tennessee where I live, there are very few options.
I agree with F3reeSpirit about the importance of your son having a stable occupation. Also having that strong social network of friends and acquaintances can bring lots of stability and quality of life.
It's hard to give advice on such a complex topic but here is mine:
If at all possible, move to a city. Your son will have many more resources and options for employment and friendship. If this is not possible, consider setting up your own group home for your son and other autistic adults. I realize these things are not attainable for everyone so I can also recommend this book which helped me and my parents tremendously.
Good Luck!
Adults on the Autism Spectrum Leave the Nest: Achieving Supported Independence - by Nancy Perry
https://www.amazon.com/Adults-Autism-Spectrum-Leave-Nest/dp/1843109042
Wow this is complicated... but to simplify... Your brother needs supported independence.
There is a lot to unpack in this topic. This book is a good start. Good luck!
https://www.amazon.com/Adults-Autism-Spectrum-Leave-Nest/dp/1843109042