Whether using “other people’s stuff” for profit is illegal depends heavily on how you acquired it, what kind of “stuff” it is (physical vs. intellectual), and how you represent it to buyers.

1. Reselling Physical Items (Generally Legal)

In most jurisdictions, including the United States, it is legal to resell physical items you have lawfully purchased. 

• First Sale Doctrine: This legal principle protects your right to sell, display, or dispose of a particular copy or product once you have legally bought it from the copyright or trademark owner.
• Retail Arbitrage: Buying items from a retail store (like clearance items) and selling them for a higher price on platforms like eBay or Amazon is legal.
• Exceptions:
  • Stolen Property: Selling items you do not own or have permission to sell is theft or “conversion” and is a criminal offense.
  • Price Gouging: Charging excessive prices for “essential goods” (like water or masks) during a declared state of emergency is illegal in many states.
  • Regulated Goods: Selling certain items like prescription drugs, firearms, or alcohol requires specific licenses. 

2. Using Intellectual Property (Often Illegal Without Permission) 

Using someone else’s creative work, brand, or invention to make money is much more restricted. 

• Copyright Infringement: You cannot legally reproduce, distribute, or make “derivative works” (like selling prints of someone else’s art or making Harry Potter-themed crafts) without the creator’s permission.
• Trademark Infringement: You cannot use a company’s logo or name in a way that suggests you are an authorized dealer or that they endorse your product.
• Reverse Passing Off: It is illegal to take someone else’s product, remove their branding, and sell it as your own without a “White Label Agreement”.
• Legal Alternatives:
  • Public Domain: You can profit from works where copyright has expired (generally works published before 1929 as of 2024/2025).
  • Licensing: You can pay for the right to use IP through a license (e.g., getting a commercial license for a 3D printing design). 

3. Business & Service Models (Legal Frameworks)

• Affiliate Marketing: Promoting someone else’s product and earning a commission on sales is a common and 100% legal business model.
• Dropshipping: Selling products you don’t keep in stock (where a third party ships them) is legal, provided you don’t engage in false advertising about shipping origins.
• Curation: Using snippets of others’ content for reviews or educational purposes may be protected under Fair Use, but this is a complex legal “gray area” and for-profit use is scrutinized more strictly. 

4. Personal Likeness & Rights

• Right of Publicity: In many states (like Florida or California), you cannot use a person’s name, photograph, or likeness for commercial purposes without their express written consent. 

Using other people’s property or creations for profit is not inherently illegal, but it is a complex area of law and highly depends on the nature of the “stuff” and the specific circumstances of its use

. Key legal concepts involve theft/conversion, intellectual property (copyright, trademark, patent), and contracts/licensing. 

When it is Illegal

It is illegal to use someone else’s stuff for profit without permission in the following scenarios: 

• Theft or Misappropriation: Selling someone’s personal, physical property without their consent constitutes theft or conversion and can lead to criminal charges and civil lawsuits.
• Intellectual Property Infringement: This is the most common legal issue. You cannot profit from someone’s original creative works (music, books, art, photos, software, designs, etc.), branding (logos, names, packaging), or inventions without explicit permission, typically granted through a license agreement.
  • Copyright violations: Making and selling unauthorized copies of a copyrighted work is illegal.
  • Trademark violations: Using another company’s branding to cause confusion about the source of goods is illegal.
  • Patent violations: Profiting from someone’s invention protected by a patent is illegal.
• Breach of Contract/Licensing terms: If an item or content was acquired under a specific agreement (e.g., a “non-commercial” Creative Commons license, or a contract with an employer), using it for profit in violation of those terms is illegal.
• False Advertising/Fraud: Misrepresenting a product’s authenticity, condition, or origin to profit from a brand’s reputation (e.g., selling counterfeit items) is illegal.
• Illegal Business Practices: Certain activities like price gouging during a state of emergency or running an unlicensed taxi service (when only permitted for non-commercial use) are illegal even if you legally own the underlying property. 

When it is Legal (with caveats)

In the United States, several principles protect the right to use or resell items in specific ways: 

• First Sale Doctrine: Once you lawfully purchase a genuine, physical item, you have the right to resell, display, or dispose of that specific copy without the original creator’s permission. This is the basis of the secondhand market (garage sales, eBay, etc.).
  • Caveat: This does not grant you the right to make new copies of a copyrighted work (e.g., you can sell a used book you bought, but not print new copies and sell them).
  • Caveat: The item must be authentic, not a counterfeit, and you cannot misrepresent the product or brand.
• Public Domain: Works whose intellectual property protection has expired or was never applied are in the public domain and can be freely used and profited from.
• Fair Use: In copyright law, “fair use” allows limited use of copyrighted material for purposes such as commentary, criticism, news reporting, or education. Commercial use tends to weigh against fair use, but is not automatically a violation.
• Affiliate Marketing: Promoting other people’s products and earning a commission for sales made through your referral is a common and legal business model, provided you have a proper agreement with the seller. 

Given the complexities, especially concerning intellectual property, it is best to assume that all creative work is copyrighted unless stated otherwise. It is advisable to consult a legal expert or tax advisor for guidance on specific business situations.