A growing number (25 percent) are for-profit incubators, which make money by acquiring part ownership in their tenant companies or from rental payments.  According to Morales, for-profit operations are expected to grow to at least half the total of all incubators in the next few years. "The future is private, for-profit incubators." he stresses.  "Of that there is little doubt.  The only uncertainty is timing," (The NBIA's Adkins, however, contends that non-profit incubators are still growing at an extremely rapid rate -- faster than for-profits -- and will continue to be a strong component of the overall mix.)

While the major goal of for-profit incubators is to make money -- they are in the business of helping young companies because it pays -- their motivation is not dissimilar to that of their tenants.  Says the owner of one: "Why are we for-profit?  Because like the people in the incubator, we're entrepreneurs, too.  It sets up the right incentives for us.  We survive because we run it like a business."

Just as incubators come in different forms, their size also varies. The largest, measured by land area, is Science Park in New Haven, Conn., with 10 buildings on 80 acres.  The Charleston Business and Technology Center in South Carolina has the greatest number of tenants -- 147 in one building.  The University City Science Center in Philadelphia consists of 1,100,000 square feet sprawled over 10 square blocks and divided among approximately 100 tenants.  Their proudest boast: graduating over 500 businesses.  In addition, California is home to the largest incubator in the Western U.S. -- the San Pedro Venture Center.