I'm certain I've posted this story before, but sometimes it's worth revisiting.
I knew a very successful working couple who had one child, a son. They worked very hard to get where they did in life, were by all accounts good parents, and came of age to plan a happy retirement.
Their son was very active with alcohol and drugs throughout high school, and continued for a few years afterwards. He refused to look for work, and was probably unemployable just the same. His parents, then retired, allowed him to live with them rent-free on the condition that he get help.
Several detoxes and rehabs later, he was worse than ever, and apparently had no intention of quitting. He didn't mind his hospital stays, as he enjoyed a very nice lifestyle by living with his parents, and because he continued to go for treatment periodically, he held up his end of this very shaky bargain.
This couple eventually exhausted most of their savings paying for their son's treatment, had to sell the dream house that they had largely built, and moved into a small apartment that they could afford. She got a part-time job at CVS and he ended up working in some office mail room, no longer able to support themselves on their retirement funds. The son? Kept on doing what he was doing. As far as they knew, he lived by couch surfing and in and out of sober living when he had no place to stay.