What tips for buying a used flute - antique and modern makes

What should one look for when buying a used flute - both keyed and unkeyed? Grey Larsen’s flute book does not touch on this subject in any depth. I suppose with antique flutes, there’s always the spectre of restoration costs. Yet, I am sure there are used flutes of recent manufacture that can develop problems over time.

This seems like such a basic question. I searched the flute forum but did not encounter any threads specifically on this topic. If I missed it, please post the link(s).