Great post/thread. I'm sure many new buyers will find this very helful. A couple of issues that I think are worth touching on:
Was it used regularly or was it a dock queen? Not indicative of much of anything. A "dock queen" may be in more original condition and lightly used, but a regularly used boat that is well cared for may be better. I'd rather have one that has been used and all problems identified and fixed.
Did the owner have regular maintenance done to the boat? Owner may have done the maintenance themself. Just because someone paid for work to be done doesn't mean it was done right.
How long has it been for sale?
In this market you can't tell anything by this. The boat may have been over priced for a year before it was reduced. May have been listed with a bad broker, etc...
If a cabin door or cabinet door doesn't open or close smoothly, it may mean the hull and deck have changed shape and causing it to bind—this can often happen if a compression post has started to weaken.
Or, it could be that the wood has expanded from 20+ years in a marine environment, etc...
Keep in mind that older boats especially are going to have problems. None are perfect. Some problems are bigger than others and some problems are big to one owner and not important to the next. It is good to identify problems and potential problems, but most all of them are repairable if you're willing to spend a few $$ and a few hours.
hunter Legend 37 Semper Paratus
Formerly - Tartan 34C Yawl