Few industries could survive, let alone flourish, amid all the negative publicity accorded to resort time-sharing over the years. Nearly every article written about resort - or vacation - time-sharing seems festooned with red warning flags about high-pressure sales tactics, shoddy maintenance, and bankrupt management companies.
Yet despite these warnings, the time-sharing business seems nearly impervious to criticism: Since 1975, its first year of appreciable activity in the United States, industry sales have swept from $10 million to an estimated $1.5 billion this year. In the last five years, sales have grown at an average rate of $300 million a year.
The number of people owning time shares has jumped from 10,000 to about 350, 000, according to the National Timesharing Council, the industry's trade group.
The time-share salespeople, then, must be doing something right. While many buyers have had problems, and in some cases lost their money, federal officials concede that most time-share companies are reputable firms selling a good, though expensive, product.
What they are selling, basically, is the right for a customer to stay in a resort for one or two weeks a year. For prices ranging from about $4,000 to more than $15,000, the customer buys the right to use the condo or hotel for a week or two every year for the next 25 to 40 years, or life. Buyers also pay an annual maintenance fee, usually ranging from $150 to $300 for each week they ''own'' their time-share resort. Combining this fee and the lost income from the money put into the time share, of course, would usually provide enough to pay for a fine vacation in a different location every year.
Despite the expense and the warnings, many people have read some of the articles, heard and thought about the words of caution, and still think time-sharing beats another vacation suspended in a backyard hammock. If you are one of these people, and are fairly certain you want to vacation in the same place almost every year, there are a few things to consider before putting pen to dotted line:
* Most time-share buyers have first been approached by developers or salespeople. People who like the idea of time-sharing may want to make the first move and find out what time shares are available in places they want to go. If you have a yen for skiing in Colorado or swimming in the Caribbean, for instance , you can get the names of many resorts and condos through one of the three exchange companies that arrange computerized ''swaps'' between time-share customers in various locations.
- Interval International, 7000 SW 62nd Avenue, South Miami, Fla. 33142; (305 ) 666-1861.
- Network One, 120 Delaware Avenue, Suite 103, Buffalo, N.Y. 14202; (716) 842-2525.
- Resort Condominium International, PO Box 80229, Indianapolis, Ind. 46280.
* Do not buy a time share with the idea that you can make frequent exchanges with someone else. The ability of these three firms to always find a suitable exchange partner has not been proved on a wide scale. Moreover, these firms charge $35 to $39 for their service, plus a similar membership fee. You should buy a time share with the idea that you are going to spend well over a majority of your vacations there.
Time-sharing, says Hal Upbin, vice-president of the Interval Time-Share Association of New York, a group of time-share developers in that state, ''is for someone who vacations in the same place almost every year. It's really for the nontraveling vacationer.''
* Plan to put the time-share management through its paces, proving to you that it has a track record worthy of your purchase. investment. For time-share management, the resorts are moneymakers. The team can often make twice as much selling a time share in a unit to as many as 50 customers as it could if it sold the units outright to one family. This is an attractive financial lure to both good and bad management companies.
Many of the better-run time-share resorts are operated by companies with experience in condominium development, hotels, real estate, and office building management. Many local offices of the Better Business Bureau can help with background checks, as they been fielding a lot of the complaints related to time-sharing.
* Do not think of this as an investment. Time-sharing is too new to have a resale record, and most companies will not sell your unit for you; you would have to do that yourself.
* Have a lawyer experienced in time-sharing look at any documents before you sign. Do not sign any agreements at one of those promotional dinners or weekends set up to introduce you to the resort. Insist on taking the papers to your lawyer first. Also, if the salesperson makes any oral promises that are not in the contract, be sure he writes these down, too.
* Be sure the contract contains ''nondisturbance'' and ''nonperformance'' clauses. The first protects you against any claims by a third party that could keep you from using the unit. The second protects your rights if a third party, such as a bank, buys out the contract.
You can get more information by writing the National Timesharing Council's American Land Development Association. For its booklet, send a stamped, self-addressed business-size envelope to ALDA at 1000 16th Street NW, Suite 604, Washington, D.C. 20036.
The Federal Trade Commission also publishes a list of time-sharing tips. Write the FTC's Office of Consumer Education, 600 E Street NW, Washington, D.C. 20580.