Some financial twists in having grown children stay or return home

Pressed by the economy, the poor job market, and high mortgage and interest rates, more and more young adults are postponing leaving home after finishing school - or have returned to live under their parents' roof.

Jean Bischmann, supervisor of family financial counseling at United Charities in Chicago, acknowledges the trend. ''We've seen people in higher economic classes, some with bachelor's and master's degrees, returning home. We find kids staying on sometimes for three or four years. In these cases they just never left, and generally these people have never discussed paying their parents anything.''

This pattern, affecting millions of adult children, was first discernible in the early 1980s as the economy entered the recession. New York University economist Emanuel Tobier explained, ''Entry-level housing costs have gone up sharply, whereas entry-level wages haven't gone up as fast.'' He says entry-level wages will go up, but probably not till the end of the 1980s.

By the end of March 1983, noted Steve Rawlings, a family demographer at the Census Bureau, there were close to 22 million adult sons and daughters living in their parents' or relatives' homes, compared with about 18 million in 1970. This was nearly a 50 percent increase, but in relative terms the increase was more moderate: The proportion of 18-year-olds living at home in 1970 was 11 percent, compared with 13 percent today.

It is seldom by choice that adults stay at home. ''Usually what we see is that the emancipated child is working on the beginning of his or her career, but the financial facts are, they have been unable to accumulate financial worth sufficient to make a down payment on a condominium or house,'' says Gordon Ramsey, tax partner in the Los Angeles office of Coopers & Lybrand, the accounting firm.

Alternative financing developments, such as methods under which young people can make little or no down payment on housing and defer payment on the principal five to 10 years, have been introduced. ''But unfortunately,'' says Mr. Ramsey, ''the tendency is to look at that balloon payment as far away when in fact it is quite close in the larger scheme and the principal payment due becomes a sticky point.''

As a result, young adults are unwillingly driven back to their parents' home or delay leaving it. ''In order to solve the instant problem, parents say, 'Come in,' '' Ramsey said. ''By and large it doesn't work well because of differing life styles.''

Financial planners such as Coopers & Lybrand are counseling parents to consider buying a condominium or house, renting it to their children at market rates, and then depreciating the value of the property. That method takes advantage of recently enacted accelerated depreciation schedules. A recent tax court case held that parents can depreciate property when the amount of rent is discounted by 20 percent off the fair market value.

Parents can also pass money on to their children tax free. Over a period of years, for instance, a parent can give each child up to $10,000 a year without having to pay a gift tax. If a son or daughter is married, and if both parents give $10,000 to each of the two young people, $40,000 can be transferred: $10, 000 times two parents times two young people.

If the gifts go over those amounts, the parents can use a portion of their ''unified credit'' - defined as a credit against the unified transfer tax (formerly the estate and gift tax). In 1984 this credit amounts to $325,000.

If you have an adult child relying on you for support, can you claim the child as a dependent? Not if he is over 19 years of age and earns more than $1, 000 a year, unless he is a full-time student. In that case, the son or daughter could be claimed as a dependent by parents even if the gross income exceeded $1, 000, regardless of the child's age.

Parents supporting a returning child can also deduct certain medical expenses on their returns. And there is a special tax rate schedule for what are called ''heads of households'' which allows some single parents to employ tax rates lower than other single people. There are two basic requirements: The child must be single, and must live with a single parent all year. The break is available even if the parent can't claim the child as a dependent.

Family counselors stress that problems apt to crop up in the sharing arrangement can be avoided if the issues are discussed beforehand. Talking openly about budgeting, shared responsibilities for housework, and space arrangements within the home can help eliminate a lot of potential difficulties later. ''If you clear all that up, you don't have resentments building up over expectations that haven't been discussed,'' says Ms. Bischmann.

Experts are agreed that adult children whenever possible should pay room and board even if it's not needed. If they don't, the danger is, as Ms. Bischmann puts it, ''Johnny may decide it's more comfortable and not leave. Where else can he live for nothing?''

And multiple living situations should not remain static. ''There need to be reviews at periodic intervals so there can be room for shifts in the plan originally agreed upon,'' advises Ed Krehmeyer, director of family financial counseling at United Charities.

Although the phenomenon of multigenerational living is widespread, some economists predict the trend will prove temporary if the economy continues to improve.