There are many pros and cons about steel boats, and while I have beenh mostly discouraged by thye steel sailboats I have seen, I just recently saw a fine one that was built in Canada. My one serious question about it was the hardness of the steel. I was hired to install a windvane self steerer, and though I've worked with steel my whole life, I was truley surprised by the hardness and toughness of this boats 1/8" thick skin. My concern was that it might, possibly, be a victim of it's own toughness along the welds and may have hardened unduly during construction, allowing for catastrophic splitting of the seams in a big blow some years down the road.
There is far too much to learn about steel boat construction and condition to discover it here, but if you want one, here are two suggestions.
1.) Get a nice plastic mallet and practice tapping steel hulls while idling arounf boatyards. It's best to tap boats for sale or when not being seen, as owners busilt painting their bottoms tend to cast a dim eye or wandering hull tappers. It will not take you long to determine if a hull has thin spots or not.
2.) Do not consider buying a steel boat that has not been surveyed by a surveyor that YOU are paying, who has previously assured you that he has steel boat credibility. At least then, you have the truth and a fighting chance.
Oh, and by the way, ask around about condensation between the hull and the boats interior structure. There's stuff to learn there.