Here's some advice to start with
I have a '75 C22. I would look at these things first. If the boat is a swing keel, look at the condition of the keel for rust and large blisters. Look very closely at the keel trunk especially where the locking pin is... (forward port dinette locker).., for any signs of damage to the keel trunk. Look at the bottom for signs of blisters. Look at all of the standing rigging, use a rag to feel the entire length of the wire to see if there are any 'meat hooks'.Look at the chain plates, preferably theve been changed out to the 1/2" upgrade.Look in the anchor locker at the underside of the deck eye. You would like to see a turnbuckle attached from the bow eye to the deck eye, to reinforce the forward deck joint.Look at the running rigging, not as critical safety wise as the standing rigging, but still important, and expensive to replace.Look for signs of water intrusion from the windows and all deck hardware.Check the tiller and rudder, you don't want to see any delamination in either.Carefully lay out the sails and look for tears , holes, missing stitching. Feel the sails and see if they feel stiff (good) or very soft and pliable (not so good).Here are some extras I'd like, and so will you. Halyards to the cockpit, roller furling, reefing capability for the mainsail, lifelines, porta potty, & whisker pole. Look at the trailer for working lights, lack of heavy rust, good tires. a bonus would be dual axles, surge brakes, and tongue extension. If you are going to sail at night, or need to use electronics, check the battery and electrical wiring system.Look for signs of major repairs from collisions. Also look for signs of sponginess on the deck and cockpit floor, because these boats have wooden cores.Things I wouldn't worry about are...The color of the paint, some oxidation to the gelcoat, lack of finish on the brightwork, the galley (most people take them out and then it requires storage space)If you just want to daysail and not park in a marina and camp out, don't worry about a pop top. You'd actually be better off without a pop top for the estra space on the cabin roof to run lines.This is getting to be the right time of year to be a buyer, because the owner is going to have to store the boat for the winter. If the boat is in less than pristine comdition, but a little bit of dirt and lack of tlc could be to your benefit when haggling a price down. If you have any acquantices who own an older C22, take them with you, because they've probably found problems on their boats and could know exactly where to look for them.These boats are well made, easy to sail and you'll love it! One word of advice when you start sailing it... reef the mainsail early, because they sail better when you limit heel to about 10 - 15 degrees. Not that there's anything to worry about if it heels more, because I think you'd have a very difficult time of having real trouble, it just makes the sailing more enjoyable to be able to sail at a consistant speed and not have to fight the tendancy to round up in heavier winds.Good Luck!