How to translate “when there’s a gold rush, sell pickaxes and shovels"? What's the Chengyu 成語 for this financial investing idiom, “don’t buy gold/mine for gold in a gold rush; sell shovels and pickaxes”?
Google Translate output “當淘金熱時，賣鎬和鐵鍬。” But I got no idea if this makes sense in Chinese. &quot;The first is, obviously, not to translate the idiom literally if it makes no sense in the target language. The translator should also keep in mind that a wordplay in one language might not be translatable into another wordplay in a different language.&quot;.
Here's the context. When There’s A Gold Rush Sell Picks and Shovels | Hatch

Sometime in my young adult life, I heard some advice that has stuck with me. I don’t really remember who said it, where I heard it, or why it came up. I do remember the message though because it was so important to an entrepreneurial mindset. The saying goes “when there’s a gold rush sell pickaxes and shovels.”
During the California gold rush, thousands of entrepreneurs and land speculators ventured out west to try and strike it rich. The truth is that most of them never struck it rich and were victim to a lot of hype and a crowded and competitive market. Gold was the glamorous business, the shiny get-rich-quick strategy. Gold was actually an incredibly risky venture because it involved buying expensive land with slim chances of it holding gold.  The entrepreneurs who made the most off of the gold rush didn’t go down that path. The ones who built great businesses were selling pickaxes, shovels, and everything else that those thousands of gold rush dreamers needed. Levi Strauss, Samuel Brannan, and John Studebaker were among the entrepreneurs who built incredible business off the gold rush, but not gold.
This advice doesn’t just apply to the gold rush. There are always going to be hot industries hot products, and glamorous opportunities that everyone and their mothers chase after. Don’t buy into all the hype. Instead find the opportunities just outside of the hype. Sell complementary goods and services instead. When demand is skyrocketing for gold, demand will also be skyrocketing for pickaxes and shovels, but (hopefully) much fewer people will be chasing those markets.
There's an article on Zhihu with the title:
淘金先富卖铲人
The paper talks about the exact phenomenon that you mention above.

Xueqiu also ran an article mentioning this adage:

有句俗话叫“淘金先富卖铲人”，出自这样的典故：当初美国西部出现淘金热时，真正能在山沟里淘到黄金的人不多，倒是向淘金者出售铲子、牛仔裤等装备器材的商家更容易发财。


It is the exact phrase that you are looking for. It isn't widely known, though, and may take the correct context to make it well understood depending on your audience.

Some other variants:

宁做卖铲人勿做挖金人

“卖铲人”

挖金子不如卖铲子

xx如同淘金客，xx人如同卖铲人 (e.g.: 游人如同淘金客，卖耙人如同卖铲人)

淘金潮里的卖铲人

淘金热中的“卖铲人”


It is quite interesting that &quot;卖铲人&quot; has become a sort of a phrase in and of itself to talk about those people who make money off of other people's pursuits.