Our postings have crossed, but I'll leave this here.
Does he go to a center like a sheltered workshop, 5 days a week, like a job type habit ?
Does he get there by public transport ?
I have experience working with developmental delay disabilities (mental retardation is the old term) in residential settings and can speak to that.
My clients (the residents) went out 5 days per week to "work" , some the "work" was activity centers, others went to sheltered workshops where they sometimes did real piecework, some went to real jobs - like your grocery bagger.
The work side of their life was to graduate to higher job levels so they could get a real job (like grocery bagger, office mail clerk, etc).
The residential side was group home, where they took turns cooking meals for everyone (12 people) with supervision/assistance/teaching of staff, take care of their own bedroom/laundry/hygiene. For some that was a good as it would get, staff were present 24/7 but the idea was to have a home atmosphere, so the home was within a normal residential neighborhood (actually a nice trendy walk to shops type area).
Some graduated to the apartment program which means staff come by to visit 1-2 times per week depending upon need. The residents here would be 4 in a 4 bedroom townhouse or 2 in a 2 bedroom apartment. Many of these residents had graduated from group homes and could take care of the simpler things in life, and of course could always phone for assistance when something odd cropped up (like neighbor cheating them, or landlord issues).