Look Carefully
Definitely have the boat checked out by a certified, reputable boat surveyor. You'll need the survey for insurance coverage anyhow. I bought a 1980 C 30 3 seasons ago, that sounds like it was in a similar situation. It had only been dry docked for a year, but it needed some maintenance. We had a survey done and found that the engine, which looked good and I was told ran good, did not have compression in one of the cylinders. It needed to be rebuilt or replaced. We ended up putting in a new Yanmar. The boat also had signs of delamination around the keel joint, this appearantly is a common feature for sail boats, but it must be repaired as soon as you see it. Our surveyor took a moisture reading and found that there was no moisture in the keel so we repaired the opening and set sail. At the beginning of last season, we discovered that the keel was separating from the boat. It was discovered that one of the keel bolts had snapped. I can't say if the delamination of the keel should have been a warning sign, but I wouldn't rule it out either. In our case it was determined that the bolt most likely snapped while we were being towed off of a sand bar in the Barnegat Bay the previous fall. Tow Boats unfortunately always want to tow from the front, pulling or torqueing you through the bar. We think that's how the bolt snapped. So we had to have the keel reset which cost about 5k. Luckily since it was determined that the towing incident caused the bolt to snap, the repair was covered by insurance. All in all, we've been happy with the boat, but it has not been without problems. We paid $11,500 for the boat and have put a a little more than that into it getting it ship shape. The new engine alone was $7k installed.