It's really hard to find any halfway houses/recovery residences through google, they are pretty much unsearchable.
Your best bet would be to contact the rehab he is currently in to see about what they can provide as far as discharge planning goes. Are there halfway houses local to the rehab he is currently at? Can they take him on a tour to one? Is there an availability for intensive outpatient, while also living at a halfway house? Structured, all male facility, close to a bus line, etc... might be helfpul. Halfway houses/sober living aren't really advertised in the internet, you would need to contact your sons rehab to see what they can offer for aftercare.
Maybe you can speak with his therapist for recommendations?
Like others on here have said, it is ultimately up to your son, BUT it can be important for therapist and family to collaborate in order for your son to get the best aftercare that will be conducive to recovery. Sometimes the therapists recommendation can only go so far, sometimes the parents boundaries, ex: "you can't come home" can be helpful for your son's therapist/discharge planner lead him in the right direction. Sometimes, insurance can help pay for a halfway house if your son is also enrolled in an intensive outpatient. There are many options out there, you just need to be led in the right direction in order to find these things out. I would recommend contacting where he currently is.
Best of luck!