Colgate Hoyt (1849-1922), an American businessman, said in 1901:
 
“Business founded on friendship is friendship endangered, but friendship founded on business is friendship assured.”
 
John D. Rockefeller (1839-1937) is usually credited with the line. However, Rockefeller’s book Random Reminiscences of Men and Events (1909) credited the saying to his Standard Oil business associate Henry Flagler (1830-1913):
 
“It was a friendship founded on business, which Mr. Flagler used to say was a good deal better than a business founded on friendship, and my experience leads me to agree with him.”
 
It’s not known when Flagler said this or if he said it before Hoyt’s 1901 remarks.
 
   
Wikipedia: Colgate Hoyt
Colgate Hoyt (1849–1922) was an American businessman active in the late nineteenth century. He was a director of the Oregon Railway and Navigation Company, and one of the founders of Everett, Washington, where a main street is named after him. He was a New York investment banker who was the partner of Joseph L. Colby as Colby, Hoyt. They were active together in the organization and finance of many businesses.
 
Chronicling America
15 March 1901, Red Cloud (NE) Chief, pg. 6, col. 1:
The wisest words spoken in a recent meeting of young New Yorkers, which was addressed by three conspicuous millionaires, were uttered by Mr. Colgate Hoyt. “Business founded on friendship is friendship endangered, but friendship founded on business is friendship assured.” Half of the proposition, that fair dealing wins good will, would be assented to by everybody. But many men have had to learn by sad experience that nothing so surely transforms a friend to an enemy as the suspicion that he is viewed and used as a sort of commercial convenience.
 
14 January 1905, Cleveland (OH) Plain Dealer, “New York Daily Letter,” pg. 4, col. 4:
“Above all things,” he (Colgate Hoyt of the Ohio Society—ed.) urged, “let no man use this organization to advance his personal or business ends. When I went to New York twenty-five years ago, to try my fortunes in Wall street, an old man of experience said this to me: “Young man, always remember that business founded on friendship is business in danger; but friendship founded on business is business assured.”
   
Google Books
Random Reminiscences of Men and Events
By John Davison Rockefeller
New York, NY: Doubleday, Page & Company
1909
Pg. 12:
It was a friendship founded on business, which Mr. Flagler used to say was a good deal better than a business founded on friendship, and my experience leads me to agree with him.
 
Google Books
December 1910, The Fra, pg. XI:
BUSINESS FRIENDSHIP
AN ADVERTISEMENT BY ELBERT HUBBARD
“I BELIEVE in friendship founded on business, not business founded on friendship,” says a certain Master Printer.
 
22 August 1912, Charleston (SC) Evening Post, “Advertising Chats,” pg. 4, col. 7:
Believe in friendship founded on business, not business founded on friendship.
 
Google Books
Getting the Most Out of Business:
Observations of the Application of the Scientific Method to Business Practice
By Elias St. Elmo Lewis
New York, NY: The Ronald Press Company
1915
Pg. 373:
A friendship founded on business is a good deal better than a business founded on friendship.
— JOHN D. ROCKEFELLER.
 
Chronicling America
13 April 1922, Mt. Sterling (KY) Advocate, pg. 7, col. 1:
A friendship founded on business is better than a business founded on friendship.
 
Google Books
20,000 Quips & Quotes
By Evan Esar
New York, NY: Barnes & Noble Books
1995, ©1968
Pg. 104:
A friendship founded on business is better than a business founded on friendship.
-John D. Rockefeller