Single people have become so active in the real-estate market that they often account for half or more of the sales at some housing developments.

Singles encounter special problems in buying and owning real estate, however, and sources of authoritative advice have been scarce. A couple of excellent new books should help fill the information gap.

"The Single Person's Home-Buying Handbook," by Kristelle L. Petersen (Hawthorne-Dutton, $14.95) explores all the major points but also delves into such specialized situations as single persons who are buying together, tips for single parents and tips for those who are divorced or made single by a death.

The author, a newspaper and magazine writer and editor specializing in real estate, sprinkles the book with quotes and references from single people she interviewed while writing the book, including what she calls "horror stories" intended to help other singles avoid mistakes.

"The single buyer is all too often the pawn in a complex game whose rules are never disclosed by the major players -- seller, broker, builder, lender and providers of settlement services," Petersen writes in a preface.

Her handbook covers the familiar how-to-buy-a-home territory: Picking a good location, determining an affordable price, selecting the proper type of home from the various alternatives, evaluating a home and neighborhood, getting the best financing and dealing with settlement costs.

In addition, there are chapters on shopping for housing in the "sunbelt" states and in Southwestern boom towns like Dallas and Oklahoma City; tips on vacation housing, including the new concepts of time-sharing and house swapping; and real-estate investment opportunities for single persons.

Petersen is a good writer and manages to keep her complex subject interesting and understandable. Her book, which the publisher describes as "the first and definitive handbook" about the subject, should make it safer and simpler for single shoppers to buy homes.

"Successful Real Estate Investing for the Single Person," by Jack Cummings (Playboy Press, $13.95) is a new work by a Florida broker-author who has written several other books on real estate.

Cummings' contention is that singles need to own real estate. "As a single person you pay more tax," Cummings writes. "You carry a heavier burden than the guy who doesn't pay any tax. You need to wise up and learn the rich guy's game . . . the rich guy doesn't pay his share because he owns real estate."

As the title suggests, the emphasis in this book is on laying down investment guidelines -- the money-making possibilities in many types of real estate including duplexes, small and large apartment buildings, condominiums and recreational property, commerical buildings and even vacant land. There are chapters with such tantalizing titles as "How You Can Become Rich" and "Building Your Fortune Through Real Estate."

Special investment strategies for single women are outlined, and the author correctly points out that most of the real estate in the nation is already owned by women, although much of that ownership is by inheritance.

Other investment techniques, applicable to anyone, are also covered. Cummings devotes one chapter to pyramiding -- using the equity in one property as payment for another -- and details such sophisticated techniques as balloon mortgages and wraparound mortgages.

"There are no real secrets in real estate," Cummings writes. "It is all basic stuff."

Cummings doesn't ignore the prospective buyer who might be interested only in a place to live, however, and devotes some space to guidelines for purchasing a single-family home. Buying shelter, he writes, "should be the first place you look to when you are deciding where you should start your real-estate portfolio."

Cummings makes real-estate investing look easy, but includes enough cautions to prevent overenthusiasm.

If there is an oversight in either of these books, it is the complete lack of photographs and drawings. Singles like to look at pictures, too.