If you had your choice of paying half price for a time-share unit at a vacation condominium or paying full price and receiving a $6 watch, which would you take?

Strange, isn't it, that many people each year pay the full price and accept the "free gift," when identical units in the same resort might have no takers at thousands of dollars less.The reason, says Clinton Burr, is in the marketing.

Each year more than 10 million Americans are solicited to attend sales presentations at full price and receive an inexpensive gift, he says, while unbeknownst to them existing owners are willing to sell identical units for less.

Acting on that knowledge, Burr established the Resort Property Owners Association. "Bleeding and starving his family," the young attorney built RPOA into a 17,000-member organization in less than two years.

Saturday through Monday he inspects and rates properties for "Resort Reports," his twice-monthly newsletter, and for RPOA guides to Southeast and Southwest properties. A Northern states guide will be ready in September.

Last weekend he toured Cape Cod, Mass.; Newport, R.I.; and the Maine coast before flying home to record his data and attend to his law practice. While others bask in luxury, he works, convinced he is creating an institution.

Burr seeks to be neutral, a source of unbiased information in an industry where buyers, sellers and renters have had no basic information source. Time-sharing will grow, he says, although right now its reputation is damaged.

"It's a great way for families and seniors to vacation," he says. It matters little if they buy, or if they rent from existing owners, he says, since they can enjoy spaciousness and luxury at prices within their budgets.

His reasons: Luxury condos - resort properties with a convenant tying them to first-rate facilities such as pools, oceanfront and golf courses - are costing too much for the mass market. And the costs might rise.

The tax benefits might disappear also. Condo owners now may deduct their mortgage interest costs; and, if they rent out their units, they may claim depreciation also. Someday that might end; Congress is eyeing such deductions.

With costs high, Burr believes time-sharing, or sharing ownership of a unit with others, might benefit from such crackdowns, and he intends to be a factor in it by providing information similar to today's Mobil Travel Guides.

Time shares were introduced in the early 1970s as a way for vacationers to save through partial ownership. It was a way for resorts to survive; it was a way for ordinary folks to afford high-class accommodations.

Then came the high pressure. "Congratulations, you have won a free cruise to the Bahamas." Or maybe it was a $995 diamond and sapphire bracelet or a sports watch or a 35mm-camera or diamond earrings.

Wholesale, the cruise was worth $25, the bracelet $50, the watch $6, the camera $5, the earrings - made of industrial diamond dust - $2. For this you had to claim your prize in 10 days and present a credit card number.

Not all such promotions are phony, but many are. Burr, himself a time-sharer, knew that a greater flow of unbiased information was needed if the healthy market he foresaw were to take hold.

A current report on sales of time-share units is an example. Sales by resort developers have grown sharply in the past decade, from an annual sales volume of $281 million in 1978 to about $1.8 billion in 1988.

Startlingly, however, owners of nearly a half-million time-share units in the United States have been unable to sell their properties. For them, the market is a disaster. Even those who manage to sell often fail to profit.

At the same time, operators of the very same resorts are selling identical units at higher prices. The difference: high pressure and marketing skills.

To help correct the situation, Burr offers to put individual time-share sellers in touch with sales organizations if they write to him at P.O. Box 2395, Northbrook, Ill. 60062, or call him at (312) 236-5684.