Housing options for older Americans are multiplying. Retirement communities, once confined to resort-like spots in the Sun Belt, are appearing in greater variety and in more locations.

Financing innovations and tax breaks, too, may soon make it easier for the elderly to cash in some of their home equity without selling or moving.

"For the first time, we are looking at the design and economics of housing that is suitable for seniors," says Leo Baldwin, housing consultant for the American Association of Retired Persons.

Retirement communities are spreading because builders see a potential profit. "By the latter half of this decade, they will be the growing segment of the housing industry," says George Matters, president of U.S. Home Corp., the nation's largest home builder. The number of Americans older than 60 should increase 19 percent in this decade to about 40.2 million, compared with 14 percent growth in the general population, says Baldwin.

U.S. Home manages six retirement communities (three in Florida, two in New Jersey and one in Maryland), is building three more and plans "in the next couple of years to be in 20" says a spokeswoman. They'll be spread around the country, adds Matters because only 10 percent to 15 percent of retirees ever move far from their last home.

Wherever they are, the communities stress recreation, amenities, and plenty of peer mixing. U.S. Home's 1,700-unit Highland Lakes community, adjacent to Tampa, Fla., offers a golf course, fishing docks, arts-and-crafts areas and a 1,000-seat auditorium. "Saturday night here is like a night in the 1930s," says Martin Roberts, president of the Highland Lakes division. "These people love the Big Band sound."

They also pay for it. Highland Lakes Buyers pay U.S. Home from 49,000 for half of a duplex condominium to $78,000 for a single-family home, Roberts says. U.S. Home won't say how much it has earned from its $15 million investment in Highland Lakes, but a spokeswoman says the profit on retirement developments in general is "much better than on other kinds of housing."

Retirement housing will diversify as demand rises, builders say. Mobilehome parks aimed at the less well-heeled elderly are already sprouting up. And some communities are offering fewer amenities but more medical care to attract older retirees.

For most older Americans, however, the most vexing problem hasn't been where to move, but how to stay put. Inflation has pushed the value of existing home upward, making elderly homeowners equity rich; most have paid off their original mortgage. But many, because they have fixed incomes, can't afford rising property-tax or repair bills, so they have to sell their homes and move.

Several innovations let older people use their equity to pay those bills. In California and Oregon, seniors can postpone property-tax payments. The states get their taxes, plus interest on the deferred amount, when the house is sold or the owner dies. Wisconsin has offered home-repair loans to low-income seniors that don't have to be repaid unitl the homes are sold.

Orlin and Goldie Folwick, both 79 years old, rcently took out a reverse mortgage on their $125,000 Minneapolis home to get money to travel. Their $40,000 reverse mortgage, at a fixed 11 3/4 percent interest rate, will give them $500 a month for 5 1/2 years, minus about $70 for average monthly interest charges.

"With that extra half of a G-note, a few more goodies show up in our living," says Orlin Folwick, a retired newspaper reporter. "By the end of five years, we can remortgage or sell the home, because by then I'll probably be looking for one of those cozy places where all you do is get up, stretch, and go back to bed."

But reverse mortgages so far haven't caught on. Although the Federal Home Loan Bank Board authorized their use in December 1978, only a few savings and loans and banks in the country offer them. And two of those have temporarily stopped because of high interest rates.

Lenders find that reverse mortgages aren't profitable, says Richard Marcis, chief economist for the Federal Home Loan Bank Board, because they usually expire before interest payments build up. And paperwork expenses are high because the mechanism is so new. But Marcis adds that if the mortgage forms were standarized, with expectations clearly outlined, the approach "offers great potential."