If home mortgages have been hard to find lately, financing for real estate developments in the multimillion-dollar range has been even more elusive.

Just as home mortgage lenders are changing from fixed-rate, long-term loans to mortgages that are more flexible and responsive to swing in interest rates, the institutions that put up the money for shopping centers, office buildings and other big developments also are demanding different terms.

"Lending money long-term at a fixed rate has been a losing proposition ever since I can remember," said Gordon B. Swanson, vice-president and regional manager of Eastdil Realty Inc., a subsidiary of Paine Webber Inc., a holding company that also owns a major Wall Street brokerage house.

Swanson said that the 30-year, fixed-rate mortgage is becoming increasingly rare in real estate financing except as part of a package that gives the lender more than just a mortgage.

Swanson said his firm pioneered the concept of real estate investment banking -- bringing investors and developers together, using some money of its own or seeking funds from others. The business is "much more sophisticated" in these times of inflation, high interest rates and tight money, he said.

A developer now has to do more than decide between a 10 percent mortgage rate from one insurance company and a 9.8 percent loan from another. The name of the game is equity money -- "the difference between what you can borrow and what you need to build the project," he said.

Equity financing, unlike a mortgage loan, means that an investor takes part ownership in a project and a share in the return from the property. In some cases, Swanson said, it may even mean that the investor has 100 percent of the equity.

In the past, the developer would have owned the whole thing himself," Swanson said. "He can't do that any more."

However, Swanson said he was referring only to U.S. developers who are "classically undercapitalized partnerships or individuals -- in contrast to the big foreign development firms, including the Canadian giants whose assets run into the hundred of millions.

Equity financing deals are coming in all shapes and sizes. There is no typical form of equity financing comparable to a standard mortgage loan, although a 50-50 share seems to be a common arrangement between the investor and the developer.

Swanson said he expects to see more land lease-back arrangements, in which the investor owns the land in a project and the developer a regular mortage loan as part of the package.

This works to the advantage of the developer, since he owns buildings that are an appreciable asset for tax purposes. If the lender is a pension fund, it is tax-exempt and does not need the depreciation.

Pension funds will represent an increasing share of the money for big real estate developments in the future, Swanson said. U.S. pension funds hold a total of $500 billion in capital, he said, and this represents what is probably the biggest source to be tapped for development money.

Despite the tight mortgage money market, Swanson said, "there is plenty of money for equity financing right now, because investors see real estate as a good inflation hedge."

Does that mean Arab money?

"The Arab money is grossly exaggerated," he replied. "But the European interest is very real."

Most of the growth in equity money will come from pensions funds in the future, he said. Insurance companies, previously the traditional source of major commercial real estate loans, have been squeezed heavily by demand for policy loans, and this has reduced the amount available for other kinds of financing, Swanson said.