A survey, especially of a cored hull boat, needs to be done both in the water and on the hard, as there are some things that can not be done in the water and others that can't be done on the hard. Ideally, it would be best to let the hull sit for a while so you can get accurate moisture readings of it.. but a good surveyor can learn alot even without that. The real worry is that one of the PO did something stupid and drilled through the cored area of the hull (starts about 2' from the keel, the keel and very bottom isn't cored IIRC) without potting the hole properly.
If you do decide to buy the SC31, you'll also need to buy or make a storage cradle for it, so that it can be kept safely on land. I would also recommend taking the rig down, if you're going to keep it on the hard for an extended period of time. The mast and rigging add a fair bit of windage, and hurricanes and other storms love to use that windage to turn the boat into a domino.
The best way to move the SC31 would probably be a hydraulic trailer, like the ones used by Brownell Systems
I'd also agree that BF's idea of getting a small sailing dinghy, especially one that you can use as a tender to the SC31 might be a better idea than getting the Hunter.
Might be a bit more expensive in the short run, but will probably be cheaper to do in the long run.
Check the tabbing on the interior bulkheads, if you get a chance to inspect the interior of the boat. Chances are likely that the tabbing will be a good way to tell if it is a factory-interior or a owner installed interior. Most owner installed interiors aren't tabbed in properly from what I've heard and seen.
Damn, I wish the slips were that cheap up here... storage for both of your boats for the years is less than what mine costs me...