Leaving home is a rite of passage for teenagers and their parents. You each adjust to your new lifestyles: they are enjoying the freedom - no more prying eyes of their parents, and you have a reprieve from the late night taxi service that dominated your weekends, not to mention the mountains of laundry.
But wait a moment; they want to come back. Here? The place they couldn't wait to leave? And back come the pots, pans, sports equipment, books, bedding, and clothes that they have collected over three years at university.
Can this possibly work?
It's not what they - or you - planned. The plan was that as a new graduate they would find a well-paid job, rent a flat and save a deposit to buy their own home.
But research by the Joseph Rowntree Foundation has found that by 2020, an extra 1.5m 18 to 30-year-olds will be forced into private renting. The number of young people unable to afford to leave their parents' home is expected to rise by half a million to 3.7m in the same period.
Rents are at a premium especially in London and the south east. Demand far outstrips supply. For every room in a shared house, there can be at least 10 applicants. Sharers can afford to be choosy - and they are.
John described finding a room: "It's like going for a job interview. You are judged on your occupation, hobbies, clothes and even your haircut."
And rents are out of reach of many graduates who are repaying their student loans, as well as high fuel or transport costs.
So what's is like if your adult son or daughter comes back home? How do you learn to live together again?
My boomerang son insisted on doing his own washing - something other parents may rejoice at. But not when that meant loading the machine at 11 pm. "Don't worry Mum, it's just a quick wash," didn't placate me when I was trying to sleep and ignore the drone of the tumble drier.
It was hard to share the space with another adult, who had developed a lifestyle different to mine: I like to go to bed early and get up early. My son liked to go to bed late and get up late. One of us was always grumpy because we'd either been kept awake or woken up.
Sarah described how she felt. "I moved back home a year after leaving university: I was made redundant. It was horrendous: my parents lived in the middle of nowhere and I felt trapped in my child's bedroom as I scoured for jobs every day.
"I did offer to help but this was turned down and my mum made it clear she resented my being there."
Joanna, whose step daughter returned home after university, said, "There was a total clash of lifestyles, especially as they're still prone to all the angst, and the drunken phone calls at 4am because they've got stuck somewhere and need a lift isn't great either."
But is it all bad?
Not according to Joanna. "The bonus of getting to spend some time with them as young adults, that insight into their lives, and getting to know their friends is more than worth it."
And what about money? If your boomerang child is earning, should they pay rent?
Nancy has lived at home for a couple of years and is now almost 27. "I pay rent, and it feels like three adults co-habiting. I clear up after dinner but probably don't do as much housework as I should.
We didn't take any rent from our son. It was a hard decision, because I felt he should contribute; but he was earning very little, saving for a deposit for a rental, and clearing his student debts.
When children return home as adults it can be difficult for everyone: "Two's company, three's a crowd" applies to many families.
Sometimes, rocky marriages are glued together by a child returning, others are torn apart as adult children push against the former parent-child relationship that's sometimes recreated.
Sharing a home with an adult son or daughter works best if there are some rules and, based on what I've heard and experienced first hand, these would be my top tips:
• Agree finances as soon as possible. It's harder to start charging rent after six months.
• Consider a contribution to chores, cooking, shopping, or gardening in place of rent.
• Discuss mealtimes and bedtimes if you have different lifestyles. Maybe a compromise on some nights of the week.
• Encourage your child to keep up the independence they had by suggesting they cook a meal now and then, and do their own laundry.
Have you got a boomerang child living with you? What are the highs and lows?