These are two unrelated processes that happen to both involve the phrase "aircraft registration," and mixing them up wastes time on the wrong task.
Registration renewal
This is something only the current registered owner does, on a schedule the FAA sets (currently a three-year renewal cycle for most registrations). It is an administrative filing that keeps an aircraft's registration active and is unrelated to the aircraft's history — it does not touch accident records, liens, or ownership history. If you are not the registered owner, you have no role in this process and no need to interact with it.
A registration records lookup
This is what a buyer, or anyone doing due diligence on an aircraft, actually wants: pulling the aircraft's current registration status, its ownership history, and cross-referencing that against accident and incident records and filed liens. It requires no relationship to the aircraft at all — the underlying FAA and NTSB data is public.
Where confusion actually costs buyers something
A registration that shows as expired in a lookup is not the same thing as an aircraft with a troubled history — it may simply mean the current owner hasn't filed a renewal, which is an administrative gap, not a records red flag by itself. It is still worth asking about, since it can complicate a sale or transfer until it's resolved, but it is a different category of finding than an accident or a lien. Know which of the two processes you actually need before you start, and read an "expired" status for what it is rather than assuming the worse explanation.