Housing advice please

Hi

i have a 39 year old son. He is autistic, high functioning but with anxiety and episodes of severe depression. He works part time as a driver for the NHS. He is currently of no fixed abode living on and off in his car or a caravan with no heating or water. 
I’m trying to get him accommodation but it’s overwhelming, he’s really worried he won’t be able to afford it. The waiting lists are so long. Can anyone advise us please as to where we can go for help?

thank you