Stanley A. Young claims not to be sure how much he is worth, and he isn't offering his accountant's telephone number. When pressed for a figure, he estimates that his holdings would probably balance out to "somewhere between $10 million and $20 million."

Uncertainty on such a scale, of course, is the stuff of dreams. But even more intriguing than the size of Young's portfolio is how he came by it. He made a good portion of his money the old-fashioned way -- he earned it by starting and managing a couple of highly profitable companies. But where others might plunk these earnings into a comfortable blue-chip brokerage account and a tax shelter or two, Young has invested most of his money in a fashion befitting his career as an entrepreneur.

"Stanley is unique," says Todd Kanter, a vice-president in the Boston office of Donaldson, Lufkin & Jenrette Securities Inc., the firm that underwrote a public offering for the company Young currently heads. "He not only invests money, he gets involved in administration, advertising, public relations, and everything else. If I put him in a stock deal, he's likely to call the company and tell them how to run their business."

Running a business is a trade with which Young has his share of experience. Some 30 years ago he headed up Webster Industries Inc., a company that was among the first manufacturers of plastic garment bags and freezer bags. Later, approached by a group of bankers, Young took over the reins of a failing electronics company and turned it into another thriving plastics business.

When he had a falling out with other members of top management over the company's direction, Young bought out its consumer products division and turned it into S.A.Y. Industries Inc. Today, eight years later, S.A.Y. is a rapidly growing company specializing in plastic containers for automotive-related products (see "S.A.Y. Hey," page 130).

That initial sally into plastic bags was the first step on Young's road to the riches whose magnitude he isn't revealing. Borrowing $3,000 from associates to establish Webster Industries, he retired 16 years later at the ripe old age of 43 with an investment that had mushroomed to $3 million. A second step was S.A.Y. When the company was just getting off the ground, Young personally guaranteed $3 million to $4 million worth of bank debt. Now, after S.A.Y.'s public offering in January 1984, he estimates his holdings at more than $9 million.

Along the way, Young fleshed out his portfolio with a series of start-ups and new ventures that he meant only to invest in -- and then, as often as not, stepped in to help run. On one occasion, for example, a group of friends approached Young about investing in a nursing home: Eight people, including Young, would each put up $10,000. Shortly thereafter Young discovered that the business, whose finances he hadn't carefully scrutinized, was near bankruptcy. Rather than accept the dim diagnosis, he took charge of the operation. A year and a half later he sold the company and pocketed $40,000.

Not that everything has worked out so well. In between plastics companies, Young founded an exotic bird-importing business in the Bronx and hired a Harvard Business School graduate, who flew to New York Monday through Friday, to run it. And so he did -- right into the ground. On one occasion the birds arrived from South America frozen solid; they had been shipped in the airplane's unheated baggage compartment. On other occasions, the birds arrived safe and warm but suffering from some exotic disease. "Everyone involved was ineffective," Young recalls. "The Harvard MBA had lost control over the operation; the employees were irresponsible." Although he tried hard, Young could find no one to buy the company. One day, he got a phone call: The shop had gone up in flames, and everything had been destroyed.

Such mishaps didn't discourage Young from investing like an entrepreneur; it is, he claims, the only way to make any serious money. "Cumulatively, I've put millions of dollars into the stock market and I'd say my net from those investments is between 1% and -10%, closer to -10%," he reflects. "The only money I've ever really made has come from companies I've controlled and worked in, or those in which I took a major position and left to mature."

In the latter category, he adds, is a high-technology company into which he put some $40,000 in seed money. Several years and a major repositioning later -- the company moved from software systems for gambling casinos into the manufacture of computer printers -- Young's investment had swelled to nearly $900,000.

Like any sensible investor, Young scans balance sheets and scrutinizes products and markets. "I look for creative ideas that show the possibility of a reasonable profit," says Young, talking like a businessman but thinking like an investor. "These are usually opportunities that have not yet been explored. I look at the market size and the timing, and then I ask, 'Is this an idea whose time has come?"

But like any entrepreneur, Young tends to gamble on people above all -- and on few people as much as Edward Fredkin, professor of computer science at Massachusetts Institute of Technology.

The two go back a long time -- 12 years, to be precise, when a broker with Kidder, Peabody presented Young with a chance to invest in a computer-printer company. The company's founder had a stellar management record and Young was interested. But he told the broker that he wouldn't jump into the deal without the advice of a computer expert who understood the technology. The broker told Young he knew just the man. A few days later, as the 6'2", 275-pound Young remembers it, found himself in the parking lot of a Valle's restaurant shaking hands with the 5'11", 160-pound Fredkin.

Both men put money into the company: Young invested $25,000, Fredkin $50,000, with the latter getting a seat on the board of directors. Soon, however, both agreed that the company's founder was not one to listen to other people's ideas. Young jumped ship with a take worth 5? on the dollar. Fredkin resigned from the board of directors, but admits now that he forgot to divest himself of his holdings until young reminded him to do so a while later.

As it happened, the ill-fated venture was the beginning of a successful financial marriage. A few years ago, Young put $20,000 into a Pittsburgh computer company Fredkin was involved with. More recently, Fredkin came to Young with his latest brainchild, an invention for desalinating salt water. Young is enthusiastics: "I told the professor, 'Anything you go into, I'll go into.' I've done several deals with him and I've never lost any real money."

To Wall Street, of course, such judgment smacks of softheadedness. "The one weakness Stanley has is that he is vulnerable to long-term associates," says Kanter of Donaldson, Lufkin & Jenrette. "If you've won a place in his heart he is very loyal." Young, unfazed, responds that he is "not interested in other people's opinions -- unless they have knowledge that I don't." Fredkin, he says, "represents a superior intellect."

Now 58 years old, Young says that he is devoting most of his efforts to running S.A.Y., and has, in fact, divested himself of several holdings in order to concentrate more fully on his company. "As long as I've been a CEO, I've never been involved in a deal that's taken time away from the company I am responsible for. It's not ethical and it's just not right." Such scruples haven't stopped him, however, from looking into a building-supply company whose owners want Young to buy them out; from coming close to financing a new physical-fitness equipment company; and from expressing some interest in several of the 100 or so proposals supplied to him by the newly organized Venture Capital Network, a New Hampshire-based investment organization.

All of these, Young claims, will be "passive" investments. Other people aren't so sure.

"Stanley intends to be a passive investor," says Kanter, "but it's just not in his psyche."