Tesla sells the rights to use and license the AC generator to George Westinghouse

1888
Tesla and Westinghaus had a friendly relationship, which went beyond the usual employer-employee relationship.
When Wetinghaus got into financial trouble Tesla relinquished patent rights and saved Westinghouse from bankruptcy.

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Under the contract, Westinghose was to pay royalties of $ 2.50 per horsepower of electricity sold. By most estimates, Tesla's royalties were so valuable that he easily should have become the world's first billionaire and the richest person on the planet, by a long shot.