Let me tell you a true story about one of my friends.
His city was going to allow one permit to build a medical waste facility (an environmental friendly incinerator to destroy the wastes). He recognized the value in this, as he owned enough land to build such a facility and had the political connections to make it happen.
My friend got the permit, built the facility and hired people who could operate it. The business started off with a "roar". He told me that his ultimate plan was to sell this "plum" to a Fortune 500 company and cash out in a lovely way.
Before long, several of the waste management giants were making overtures to him. He had a problem though. He never had a handle on the true worth of his company.
Possessing the only permit in his metropolitan area made the company worth many of millions of dollars by itself. He never priced it. He decided on a buyer but there was a catch. The suitor didn't want to buy it, wanting instead to joint venture with him. That way he could get a piece of the volume forever. He took the deal and waited for his revenue share.
Boom! The partner shut the facility down forever and transferred all business to one of its out-of-state facilities. All the suit-partner wanted was to kill its new competition. My friend was devastated. He should have found the true value and sold it completely.
Word to the wise!