Many great posts here indicated that these listings don't necessarily mean the boats been on hard for many years. If it has, run away. Here's some examples of what goes wrong:
1. Anything with a gasket in it or rubber in it has dried out and likely failed. Plenty to choose from here, engine, pumps, hoses, head, etc.
2. Bedding material has dried out and failed. Everything attached to the deck is leaking.
3. Engine internals may have rusted. Engines like to run and have lubricant spread around. The engine might be damaged or frozen and unrecoverable.
4. As pointed out, all the electronics and electrical stuff is old, if anything is wrong with any of it will be hard to get it fixed, find replacement parts, you'll be replacing (although this is true pretty quickly anyway today).
5. All the auxiliary stuff you tend to get with a used boat will be trash. Life jackets rotted, spare parts and tools rusted, etc.
6. Seacocks will be frozen. If they are old style, maybe you can take them apart and grease, if not might be necessary to replace.
Boats do best when they are run regularly, and when things break they are fixed. And everything breaks. The cheap part is buying the boat. The expensive part is operating costs.
Material costs for a boat is death by a thousand cuts. The value is in everything from winches, to pumps, to rigging, to lines, to electrical, motor, hull...everything. $1000 here, $1000 there, after a while it adds up to real money. Never mind the labor associated with replacing any of this stuff unless you do it yourself.
IMHO, buy a good boat, used regularly, by a meticulous owner. Bargain hunting as a first time boat buyer will more often lead to false economies. There are exceptions to this rule, people who are really good at fixing things themselves and have lots of time on their hands to do it. It seems like a good idea until the first time you try to pull a hose off a thru hull fitting that's mounted away in a locker someplace where you need to be a contortionist to fit.