Well, my oldest is 22, and she lives 800 miles away from us. She graduated this past May, and never moved back "home". Home is in quotes, because we moved away from the area she was going to school in, rather than her leaving us, so our current home doesn't feel like home to her. She has a full-time job and shares a 2-bedroom apartment with three other people. She doesn't have a car--she uses public transportation and shares a ride to/from work with a co-worker (free if she brings a daily coffee, so a good deal for her). Just last week, the facade fell off her building, meaning she had to find other lodging for the night while the building was inspected, etc.
I guess my point is, at 22, she's a full-blown adult. I had zero luck in convincing her to move down here--that bird has flown! I understand that not every young adult is on the exact same schedule--our DS20 won't be moving out any time soon. But, it's not unreasonable for the OP's DD's boyfriend to find his way on his own at this stage in his life. If he wants to, of course, but really, that's on him. His parents have to do what works for them. If he doesn't like their choice, he's got the right to choose differently.