They were talking about real estate. It is, to be frank, one of their favorite subjects.

One had bought a house in 1973 for $40,000. It had just been valued at $265,000. Another had a neighbor who sold her house, tripling her money in 10 years. A third figured carefully the inflated value of his home into his retirement plans.They did not brag, these couples in late middle age, of having had any special prescience about a real-estate boom. They had put money down on a house in the '60s or '70s and won the jackpot of the '80s.

The houses they chose to live in were also investments to live off. They were now middle-income and house-rich. So conversations like these make them feel good or at least lucky.

But then the subject turned to their grown children. Could their children afford to buy the houses they had grown up in? A second set of stories poured out, more troubled than the first.

They had working children wholly unable to save a downpayment that might equal the parents' entire first mortgage. They had married children who needed two jobs to afford what they had supported with one. Most of their offspring were double-income and house-poor.

These days the economic gap between generations is built on the private turf of real estate. A space has grown between those who have houses and those who don't.

More people over 65 and fewer under 35 own their own homes. In 1977, 11.5 percent of new homebuyers were in their early 20s. In 1987, only 4.2 percent of these buyers were that young. More than half of new mortgages depend on second incomes.

Over the past 15 years, incomes fell behind inflation and houses sped ahead. Tax breaks have gone to those with mortgages, and so-called tax revolts made generational differences even more striking. In California, famed Proposition 19 froze property taxes at 1978 rates - but only for those who already owned homes. A new neighbor may pay vastly more than the older couple in an identical house next door.

There are other very real effects of real estate on these two generations. Generations find common ground in the family. There, the house-rich middle class increasingly is called upon to help its house-poor children.

I am told that standard equipment for any mortgage lender's office includes at least four chairs: two for the couple, two for their parents who help bankroll the sale.

If I am to judge by my listening sample, these elders feel both duty-bound and willing to share their good fortune. But another of their favorite conversations echoes concern about the long-term dependence of "kids these days."

The "kids" of 25 and 30 have in turn become awkwardly conscious of the way that real estate has solidified the two-class structure. The have and have nots of their own age are often those who either have or have not parents with home equity.

The windfall is a large component of an older generation's improved economic status. Their independence is a boon to their children as well.

But it is also a major reason why the scales are tipping. It's why there is a need to build more affordable housing, tax more of the capital gains of those who rode the real-estate boom and allot the money to help families buy into the market.

Rising real estate makes for great conversation. But a younger generation is being left out of the lucky dialogue. It looks as if the family homestead rests on shaky ground.