Middle-aged people often leave family holiday gatherings worried about aging parents. If the problems are financial, the offspring might be able to help out through housing - and get a tax shelter in the process.

Many elderly people own their homes free and clear but feel poor nevertheless because they have little cash available. Home equity loans are not the answer because the elderly often don't have enough income to meet the monthly payments.What might work better is for a son or daughter to buy the house and rent it back to the parents. The proceeds from the sale, invested, would provide cash for the parents to cover the rent.

There is a financial benefit for the son or daughter as well in many cases - rental properties are still good tax shelters for anyone with an income of $100,000 or less.

"Tax Smart, the Touche Ross Guide to Total Tax Strategy for 1988," gives an example of how such a strategy might work. The book, written by Robert Wool with the Big Eight accounting firm, offers practical tax strategies, primarily for upper-middle-income taxpayers.

In the example, Natalie, a divorced 42-year-old woman, owns a travel agency and draws a salary of $100,000 a year. She is worried about her mother, who lives in a modest condominium in Miami Beach and has an income, including Social Security, of only $15,000 a year. The elderly woman is constantly fearful of running short of money.

The Touche Ross adviser tells Natalie to consider buying the condominium - with an estimated market value of $30,000 - and renting it back to her mother. Natalie would need only about $5,000 for a down payment to make the purchase.

"Her mother would be in a new and more comfortable financial situation and be able to handle the rent easily," Touche Ross said. "She would first of all have a fresh $30,000 invested for herself, presumably returning at least 8 percent, or $2,400 a year. That alone would pretty well cover her new rent."

"So long as the condo was her mother's principal place of residence - which it would be - and Natalie charged her a fair market value rent, the place would qualify as a rental property for Natalie."

Natalie would pay no taxes on the rental income she received from her mother because she could use the mortgage interest and real estate taxes she paid on the condo to offset the rental income for tax purposes.

In addition, because her income falls into the $100,000 or less category, she could deduct up to $25,000 of "losses" from the condominium against her salary.

Under the 1986 tax law, up to $25,000 in losses incurred in a rental property - including on-paper-only depreciation losses - can be used to shelter salary income if the rental owner's income is $100,000 or less.

"The condo, in other words, could be a substantial tax shelter for her," Touche Ross said.

This $25,000 deduction is phased out at incomes between $100,000 and $150,000 and disappears entirely above $150,000.

Touche Ross also told Natalie that if all the rules on rental property were too complicated for her, she could simply buy the condo from her mother and let her live there rent-free. The condo would then count as a second home for Natalie for tax purposes, rather than as a rental property.

Of course, without rent from her mother, Natalie would have to make the mortgage payments out of her own income, but the mortgage tax deductions available for a second home would offset some of that cost.

These ideas are worth considering as the 1989 tax season approaches. Ideally, they could be of benefit to both parent and child.

(Pamela Reeves writes a weekly real estate column for Scripps Howard News Service.)