Based on what I have learned from the transom rebuild on Shearwater I would do more than just a visual inspection if doing my own survey.
There are some pretty easy things that can be checked without having a meter or drilling holes.
On the visual part look closely at
screwheads, see if there is sealant around the head and behind what it attaches to. Inspect the transom drains, motor bolts, kicker bracket, and cleats for sealant
Look for light rust stains on the gelcoat around the railing screws and any brackets. Could be cheep stainless or a damp core under the screw will have the same effect
Take a screwdriver and a tube of good sealant if the owner will agree to let you pull a couple of screws or best case they should do it for you.
Remove some screw from the lowest point on the transom, inspect the screw for any rust and the hole for sealant or better yet see if the hole has been epoxy lined (tough to do without removing some part completely)
Be nice to check both sides at a minimum
Do the same for say one of the fuel tank screws (these seem to be an issues on the 22) and a L bracket
If it is attached to a cored part of the boat it needs to be sealed and goop is the traditional way but should be redone every other year at the most. Really should be epoxy lined with sealant.
Your are lucky to have a resource like the C-Brat site to assist, there are a number of areas on the 22 that come up frequently. L brackets, fuel tank mounting screws, keel guard screws, anchor locker drains. I do not own a 22 but these are the ones I remember.
Don't forget the electrical, at least check out the condition of the main panel for what it looks like, neat is always good, birds nest not so good.
Good luck and hope you get the wife on board so to speak
stevej