Two new concepts -- one of which was picked up and promoted this week by the Federal Home Loan Bank Board as an alternative to conventional financing -- are breathing life into a stagnating real estate market in this Sun Belt city.

Advanced Mortgage Corp. unveiled one of the concepts, an appreciation participation program, in mid-September. (The bank board this week promoted the concept, calling it a shared appreciation mortgage or SAM.) Under the plan, the company offers conventional home mortgage loans at interest rates one-third of the home's appreciated value when it is sold.

Harrison Gentry, an Advance regional vice president, said Phoenix is a pilot city for the program, along with Washington, Baltimore, Atlanta and Denver. The company hopes to provide $300 to $400 million in mortgage money nationwide, with $50 to $60 million slated for Phoenix and Denver.

Initial response in Phoenix has been "phenomenal," Gentry said, with the company averaging 200 to 300 daily inquiries. Numerous Phoenix homebuilders are interested in "buying all (the mortgages) we can give them," Gentry added. Realty World is the real estate firm picked to market home resales under the program.

"This program is helping a lot of people who can't qualify for mortgage loans or can't afford a home because they can't keep their monthly payments down," Gentry said. "It's making housing available to people who couldn't otherwise afford it. They don't give up a whole lot.

"What the consumer saves on the front end in payments over the first five years comes close to the appreciation he'd give up (when the home is sold). If he sells the property in a down market, he could break even.

"The (mortgage) investor is assuming the greater part of the risk. He's betting the market will appreciate. That's why we're letting them pick the city they want to invest their money in."

One Phoenix homebuilder, A. J. Littman, has come up with another concept to bolster the real estate industry. Littman's Equishare of Arizona Inc. aids home buyers by paying 25 to 75 percent of the home's cost in return for a comparable share of the equity buildup at time of sale.

Equishare doesn't float the mortgage loan. The company actually becomes a "tenant-in-common," qualifying for the loan with the home buyer or "resident owner." The resident pays for routine maintenance and utility costs while the company shares major repair costs. The resident also pays the company monthly rent for utilizing the company-owned share of the home.

As a result, the savings in monthly costs are not as great as under the Advance program. Littman says he is aiming to attract first-time home buyers who need cash for a down payment as well as people who want to live in more expensive homes than they can qualify for. Realty Executives markets the program in Phoenix.

Equishare is patterned after similar California and New Jersey plans. It, too, relies on outside investors and currently is offering 1,200 units of limited partnership interests priced at $1,000 each.