Hi, there.  Have you tried calling your county's social services department and asking for help?  I understand about the worrying and it's very nerve-wracking to live with that fear, as I did with my son for years.  He did attempt suicide twice, but we were able to get him some help and he already had a therapist.  Once he was 18, we even got some assistance from the county for his hospital bill because he didn't have a job.  Most counties also have mental health clinics which charge on a sliding fee scale, so your son may not have to pay anything.

The other thing is that you need to let go of some of this worry and realize that there is only so much of this that you have control over.  It's a very helpless feeling.  I hope you are able to find some place to help him and if he actually is suicidal, you could take him to a hospital emergency room and have him committed to a psychiatric unit for 72 hours while they make an assessment and from there, you're likely to be referred for help.

I wish you all the best; please feel free to write here any time.  Wish I had a magic wand that could make this all better for you.