My son has his future planned and it doesn’t include university and a career. He’s waiting to inherit the house and become a landlord

When Zac was born, it occurred to us that the age gap between him and his siblings (he is six years younger than Jake; eight years younger than our twins) would mean that one day he would, in effect, be a single child. We gazed down at our baby blowing milky bubbles in his cot and worried that, in the future, once his brother and sisters flew the nest, he would feel isolated and deserted.

Ping forward 18 years: the future is now the present, and it is not what we imagined. Instead of being an only child, Zac is still surrounded by his siblings, crammed into the same bedrooms they had as children.

When the three elder siblings went to university, they believed they would move out permanently straight after, clutching degree certificates, heading for a place of their own, renting first perhaps, then hopefully getting a mortgage. Zac does not share this dream. He has seen the others leave, only to return home. He has learned that a degree doesn’t guarantee a career. It has made him wary of going to university, reluctant to take on debt.

Those six to eight years between Zac and his siblings mean that he is of a different generation. He doesn’t expect to be moving out in the near future. He also has a very different take on acquiring property.

“I don’t need to have a career,” he says. “I can just become a landlord.”

I give him a blank look.

“When I inherit my share of the house,” he explains. “Then I can rent out a room or a floor or whatever.”

When I was a teenager, staying at home with my parents after leaving school would have been a sign of failure

“But Dad and I have to die first,” I exclaim. “We’re not expecting to do that in the very near future … I know it’s a dead cert that it will happen eventually …” I fumble for a joke. “But I’m hoping not yet.”

The inscrutable look he gives me makes me wonder if I shouldn’t be careless enough to stand at the top of a long flights of stairs. When I repeat his words to my daughters, they are scandalised, immediately berating him. “How could you be so thoughtless? You’ll be sorry when they do die – just so you can get your hands on some property!”

But my youngest son isn’t alone in his thinking. According to an analysis of recent ONS data, about 100,000 twentysomethings believe they will never move out of their parents’ home – many of them considering that their best bet of owning property will be to inherit it. I consult Jake. He is the fiercest of the four siblings in his determination to move out, declaring loudly and often that, “After my MA is over, there’s no way I’m staying here being a freeloader.” But when I ask if he thinks he will buy a property one day, he shakes his head. “I can’t see a time I’ll be able to afford my own place.” He nods when I tell him about Zac’s plan. “Lazy bugger. Yeah, I expect the only house I’ll ever own is yours, but,” he gives a broad smile, “unlike my brother, I’m not waiting for you to die to get my hands on it. There’s a reason I’m your favourite child, right?”

All of this, I realise, isn’t a temporary glitch. This is the new normal. I’m still wrestling with the concept, because when I was a teenager, staying at home with my parents after leaving school would have been a sign of failure. I had also imagined that, like my parents, I could shrug off financial responsibility as soon as the kids reached 18. But Ed and I have never been as burdened with expense as we are now. Six adults to feed. A house to run. That same house that we thought might be our pension, already being turned into a useful income in the mind of our youngest son.

“At least he’s thinking ahead,” says Ed says.

Meanwhile, I point out to Zac that it is in his best interests to protect his assets, so he should remove the 20 dirty cups festering under his bed to stop the spreading fungus destroying the timbers of his future goldmine.

Amazingly, he does. Balancing a tottering pile of filthy cups, he pads into the kitchen, where he leaves them next to the dishwasher.

Some things never change.

• The Stranger by Saskia Sarginson (Piatkus, £7.99). To order a copy for £6.79, go to bookshop.theguardian.com or call the Guardian Bookshop on 0330 333 6846.

Names have been changed