仕入れ and 購入: purchasing stock for sale and purchasing generally
Read the stock-for-sale purpose of 仕入れ alongside the broader action 購入. Both descriptions can apply to the same purchase.
Going out to purchase stock
仕入れ, read しいれ, means purchasing stock. 店主は朝早く市場へ仕入れに出かけた。 says that the shopkeeper went to the market early in the morning to purchase stock for sale.
店主 identifies the actor and 仕入れに the purpose of going out. The trip is reported, but a completed purchase quantity is not supplied by this sentence.
The broader purchase action
購入, read こうにゅう, refers to purchasing. 新しい自転車を購入する前に何台か試した。 says that someone tried several bicycles before purchasing a new one.
購入 alone does not provide a resale purpose for the bicycle here. Read the intended use from additional context.
Two perspectives on one purchase
季節によって野菜の仕入れ価格が変わる。 says that the procurement price of vegetables changes with the season. The price concerns buying the stock.
A shop's purchase of vegetables to sell is also a purchase in the broader sense. Look for the stock-for-sale purpose instead of making 仕入れ and 購入 mutually exclusive.
If a shop uses 仕入れ to describe buying vegetables to sell, is calling the event 購入 necessarily wrong?
Show the answer and why
No. Both can apply to the purchase. 仕入れ makes the stock-procurement purpose explicit.