We payed for our son's IOP a couple years ago when he was 19. I don't remember him going all day, every day.
He did learn all of his recovery tools there. Each time he relapsed after that, he knew where to go and who to call when he was ready to join the living again.
One thing I would do over is have him move into a sober living environment after IOP. The structure, curfew, mandatory meetings, mandatory work, etc, seemed to help my boy alot.
I took him back in after each "bottom" and we had a 4 month on 2 month off cycle repeating for a couple years. I kicked him out 3 times.
Last time, we all agreed that an SLE would be a better option.
He has been in a very active recovery for a little over a year now. He even has 3 sponsees.
It's very comforting for now, but I know he's one bad decision from throwing it all away. That's why I still read here several times a week.
IMO about the job thing: If he is doing full time IOP and working an active recovery, let him do just that if you're willing to carry him financially for a little while longer.
If it's part time IOP with meetings here and there, a part time job would be in order.
The key part in this lies in the boundaries you create for your own recovery.
I was addicted to my addict. Probably still am. Just way more educated about the process now.