I do understand what you say in next post. But, it hard to reach the one boat point for myself without seeing the bottom.
I set a guideline I follow for boats as to survey or just look myself. But, either way, I really want to see the bottom.
I am interested in an old 21' swing keel for something to play around with this summer, probably give it away in a few years.
This a $500 boat. I will still pull it out of the water (no cost) to see if the original keel still there or a piece of plate steel.
This way I have some idea if the boat at a point I not spend much to test some ideas I have and enjoy it.
Heck, if the Hinge Pin on the keel all worn out, may offer $300, it could cost $100 or more to fix, doing it myself (depending on this and that stuff).
But, best I know is look everywhere you can. Take a flashlight and large washer/rubber mallet for taping around. Also, this may sound stupid, but, I have a small monocular. I can eyeball the standing rigging for frays and whatever I can spot.