This law is not about “making” people depend on you.
It’s about being so indispensable in what you do, who you are being and in what you offer, that they see you as the only choice to help them. 
In doing so, you can avoid the fate of the condottiere or Italian mercenary soldier in our next story.
~ Courtesy of The 48 Laws of Power by Robert Greene
Sometime in the Middle Ages, a mercenary soldier (a condottiere), whose name has not been recorded, saved the town of Siena from a foreign aggressor. How could the good citizens of Siena reward him? No amount of money or honor could possibly compare in value to the preservation of a city’s liberty. The citizens thought of making the mercenary the lord of the city, but even that, they decided, wasn’t recompense enough. At last one of them stood before the assembly called to debate this matter and said, “Let us kill him and then worship him as our patron saint.” And so they did.
The Count of Carmagnola was one of the bravest and most successful of all the condottieri. In 1442, late in his life, he was in the employ of the city of Venice, which was in a long war with Florence. The Count was suddenly recalled to Venice. A favorite of the people, he was received there with all kinds of honors and splendor. That evening he was to dine with the doge himself, in the doge’s palace. On the way into the palace, however, he noticed that the guard was leading him in a different direction from usual.
Crossing the famous Bridge of Sighs, he suddenly realized where they were taking him — to the dungeon. He was convicted on a trumped-up charge and the next day in the Piazza San Marco, before a horrified crowed who could not understand how his fate had changed so drastically, he was beheaded.
Such is the fate, (to a lesser violent degree, one hopes) of those who do not make others dependent on them. Sooner or later someone comes along who can do the job as well as they can – someone younger, fresher, less expensive, less threatening.
Be the only one who can do what you do, and make the fate of those who hire you so entwined with yours that they cannot possibly get rid of you.