“Buy low, sell high” (Wall Street proverb)

“Buy low and sell high” is a sure way to make money. The exact origin of the saying is unknown, but the concept is simple enough. The “buy low” (or, “buy at a low price”) and “sell high” (or, “sell at a high price”) phrases are both cited in print by at least 1826.
 
   
30 March 1826, Baltimore (MD) Patriot, pg. 2, col. 2:
It was the business of all merchants to buy low and sell high.
 
8 August 1837, Richmond (VA) Enquirer, pg. 2:
The merchants, who are the great customers of monied corporations, as their interest is to buy low and sell high to the people…
 
Google Books
5 April 1838, Extra Globe, pg. 19:
This is the manner inwhich this great influential, aristocratic, federal phalanx make overgrown fortunes; they buy low and sell high; they have the perfect control over all the banks, and fleece both planters and country merchants.
(...)
Franklin (La.) Republican
 
15 June 1843, Wiskonsan Enquirer (Madison, WI), pg. 1, col. 5:
To buy low and sell high, (to a qualified extent,) in his business—his legitimate calling, and, to accomplish both these objects, he must look to statistics of supply and demand—in other words, to production and consumption—the bases of all trade.
   
25 August 1851, Boston (MA) Daily Courier, pg. 1:
The people are beginning to learn that they cannot rely upon the quotations of stock in the market at Boston, managed by stockjobbers and speculators, whose sole business (it would seem) is to create panics and fluctuations, so that they can buy low and sell high.
 
12 October 1893, Atlanta (GA) Constitution, pg. 8, col. 1 ad:
Advice to those who want to get rich. Buy low and sell high.
GEO. S. MAY,
Care May Maniel Company.
   
Google Books
The A B C of Stock Speculation
By Samuel Armstrong Nelson
New York, NY: S.A. Nelson
1903
Pg. 208:
In a traders’ market buy low — sell high.
 
11 February 1903, Philadelphia (PA) Inquirer, pg. 4:
SHEARING OF
THE LAMB
How the Speculator Is Fleeced in
Wall Street—Buy Low and
Sell High
   
Google Books
Banking and Currency
By Ernest Sykes
London: Butterworth & Co.
1905
Pg. 193:
In dealing with bills drawn upon countries which London quotes in shillings and pence to the foreign unit, the exact reverse of this is true, and the rule to be remembered is the usual commercial rule for buying and selling commodities: “Buy low, sell high; the better the bill, the higher the rate.”
 
Time magazine
Buy Young, Sell Young
By Barbara Cornell
Monday, Sep. 04, 2000
His buddies were intrigued by Microsoft after the antitrust ruling, so he went online to snap up stock. The price jumped $20 a share. It was a classic case of right place, right time. Except that Jason Marchione is not your classic investor. His lucky tip came in the middle of fifth-grade computer class. “There’s that famous quote,” says Jason, 11. “Buy low. Sell high. Make mad dough.”