They need to decide, for example, what household items are shared, who should pay for what and what kind of lifestyle for their grown-up children parents should help support.
Two in three single people in their 20s are now living with their parents, which equates to about three million men and women.
Loughborough University’s Centre for Research in Social Policy investigated what families such as these need as a minimum to live on, and what determines their living standards.
The research, Family sharing – A minimum income standard for people in their 20s living with parents, talked to both young adults and parents living in such households, discussing present-day norms of how they share living arrangements and expenses.
It found that living with your parents in your 20s is seen as a normal expectation, without stigma, for young adults today.
The high cost of renting or buying independent accommodation, and in some cases the desire to save up to achieve such independence in the future, were seen as the driving forces for living ‘at home’ with parents.
Living together means saving together
The study, funded by the Joseph Rowntree Foundation, found that such families make large savings from living together.
Overall, the minimum cost of living* for a single person and their parents was calculated as £135-a-week less living together than living separately: minimum weekly costs are £303 for a single person renting their own flat, £472 for a couple renting a family home with an empty room (a total of £775), or £640 for these three people living together.
The biggest saving was rent, accounting for £91 – other savings came mainly from council tax and utilities (£30) and from household goods (£7).
The main effect of these savings is to make life much cheaper for the young adult: typically, parents buy most shared household items such as food and household goods and cover the cost of accommodation.
Both parents and young adults in the study thought that it was fair that a son or daughter who is earning should make a contribution towards board but said that there is no consistent basis on which to determine the level of this contribution, which would vary with the financial circumstances and attitudes of those involved.
The study found that without a board contribution, the cost of having a grown-up son or daughter at home adds an estimated £24 a week to parents’ expenses, so a board contribution of at least this amount would be needed to avoid them being out of pocket (this can be seen as a contribution allowing parents to break even).
This does not include the cost to parents of living in larger accommodation than they would need than if they down-sized after children grew up and left home.
However, participants in the study felt that most parents would want to keep a home large enough for their children to come back to if necessary when they were still in their 20s, since unstable living and employment arrangements could fall through.
Move out: Double the cost of living
For a young adult contributing enough in board to allow their parents to break even, overall living costs are 45% lower than if they rented a flat independently.
This reduces the amount that they would need to earn to achieve a minimum standard of living from £18,000-a-year renting their own flat, to £9,000-a-year living with their parents.
Katherine Hill, lead researcher on the project, said: “This kind of sharing can bring big savings to families, and make it easier for a young adult to make ends meet than if they lived independently.
“However, those who feel they have little choice but to live with their parents may need to make compromises around privacy and independence.
“Our research showed that it can be difficult for families to find satisfactory ways of sharing costs and other arrangements, where relationships are based more on emotional ties rather than formal negotiations.
“Parents want to help their sons and daughters to save money, but do not want to be taken for granted or delay them taking financial responsibility.
“And while parents who own their homes and have a good income may have sufficient resources to help reduce costs for their grown-up children, parents on lower incomes can struggle to do so, and may have different expectations about who pays for what."
Professor Donald Hirsch, Director of the Centre for Research in Social Policy, added: “We talk a lot about living standards for single people or for families with dependent children, but not as much about families where grown-up sons or daughters live with their parents, about which there has been little prior research.
“This is becoming a distinct phase of life for many families, which can last several years. What happens in these years affects not just the lives of people in their early years of adulthood, but also the well-being of parents.
“It can extend the time that they devote resources to their children, which can potentially create difficulties for families on low incomes and for parents who are entering retirement.
“In particular, the expectation that parents will maintain a family-sized home well after their children become adults can mean that they may need to rethink retirement plans.
“Over the long term, more people are expected to reach retirement as private tenants rather than owning their homes, and this group will find it hard to maintain a high rent for a family home when no longer earning.”
The study was based on a series of five focus groups with adults aged 20-30 living with their parents, and with parents living with their sons or daughters aged 20-30, which took place in 2018.
*The minimum cost of living on which these findings are based refers to the Minimum Income Standard (MIS). This is an amount calculated for each family based on what members of the public think you need to meet your material needs and participate in society. Further details of the MIS research programme carried out by the Centre for Research in Social Policy can be found here.