A couple of points:
Steel boats usually rust from the inside out. The design is important, but it's the builder who usually makes it or breaks it. If the builder builds it right, and coats it right while under construction then much of the interior rust problems are postponed. My boat is 15 years old and has very little interior rust. My surveyor says I should thank the builder. So, find out who built this boat and check out their reputation. If they're still in business, go see them and ask them about the boats they've built. Then find the owners and ask them what their experience has been. If the builder has build lots of steel boats, it may be OK. If they build a few every now and then, be careful.
Inside rust is usually harder to fix than outside rust because it's so much harder to get to. IMO, covering rust ("sealing it up") doesnt work -- you've got to grind it out (or sand blast it out), chemically treat what you can't get out and then recoat it using a high quality paint system, which will ususally be some mix of an etching primer, expoy primers (multiple coats) and top coats, often urethanes. Do everything right and it can be good as gold, but sometimes even when you do everything right, the rust comes back. The only way to inhibit rust is to get rid of all the oxygen. With steel boats you do get higher strength, but higher maintenance comes with it.
When you've finished kicking the tires and are starting to think seriously about it, you'll need to find a good surveyor. I'd go to someone who doesn't have a dog in the fight to get recommendations. Ask around -- ask at the bigger boat yards, mechanics, riggers, etc. Find someone who regularily surveys steel boats and make sure they have a professional certification. I think you can find websites of the marine survey associations and they will point you to people in your area. The survey will cost you many hundreds, so wait until you're really serious to take that step.
I'd second Cam's point re the broker. He's blowing smoke. I've been told that the rule of thumb with standing rigging is "watch it closely after 10 years, be thinking about replacing it at 15 years and do it by 20". There's no way you get a new rig for $2K. I've heard that the old SS wire is often better than the stuff you get today, but, I'd be really careful when it comes to reusing anything. One of the more famous riggers in the world is in Port Townsend, Brion Toss, (see Brion Toss Yacht Riggers, Sailboat Rigging
). Give him a call, see what he thinks. The people at Port Townsend Rigging are also excellent (Port Townsend Rigging: Services and products tailored to your sailing experience
). Rigging is not a DIY type of job. If you mess up and it comes down, people can get killed. Let professionals do the rigging.
Last point, it's fun working on boats, but it can get old. The idea is to go sailing. If you spend too much on a boat that needs a lot of work and has so many projects that you can't afford to have the yard do most of them, you'll never go sailing. You can prevent that by buying a less expensive boat, or a smaller one that's been loved a lot.