Checking what you are actually buying
Start with title. Assignments from each inventor to the seller should be in writing and ideally recorded at the USPTO, and gaps in the chain are common in startups and university spinouts. Confirm that maintenance fees are current, since a lapsed patent may or may not be revivable. Look for existing licenses, covenants not to sue, security interests, and commitments made to standards bodies, because those encumbrances usually travel with the patent. Some patents are linked by terminal disclaimers that require common ownership to stay enforceable, which affects whether you can buy just one of them.
Value and validity
The price usually reflects what the claims cover today and what pending continuations might still cover. Review the prosecution history for statements that narrowed the claims, any earlier litigation or USPTO challenges, and whether the claims read on products actually on the market. Prior art searching and an eligibility review can reveal weaknesses the seller has not mentioned. If you plan to assert the patents, consider whether past licenses or settlements limit whom you can pursue, and whether the seller and its licensees marked their products properly, which can affect past damages. Remaining patent term matters too, because a patent near the end of its life offers less to enforce or license.
Structuring the deal
A patent purchase agreement covers the assignment itself, the transfer of files and prosecution records, cooperation from inventors, representations about title and encumbrances, and what happens if those statements prove wrong. A license back to the seller is common and should be scoped carefully. Recording the assignment promptly helps protect you against a later conflicting transfer. Bring the patent list, the seller's materials, and your plans for the patents, whether that is product protection, licensing, or defense. We set the diligence scope to match the price and the intended use.
