Do not be fooled by a clean-looking boat, because what's inside might not be quite as nice. There are a few key things you should always watch out for when purchasing a new boat.
The first step would be to check electrical wires and connections such as ring terminals, butt connectors, and lugs. Check behind panels or monitors at the helm if you can. What you don't want to see are connectors with bare wire visible as it will corrode in the wet and salty marine environment. Cheap wiring is a nightmare when it comes to replacement.
While you are near the battery, take a look to see if there any acid spills on or under the battery -- this could be an indication of battery problems. Then look at the fasteners used at the batteries. If you see wing nuts, it's not a good sign. There should always be a regular nut, a lock washer, and a washer on a battery post because wing nuts can come loose. All wing nuts on electrical connections should be replaced as soon as possible.
Finally, go around the boat and open every little hatch to account for hidden issues. Verify the bilge water level. Also, look at how cables are routed from the aft to the bow. In some cases, the only route from the batteries to the cabin is a single tube full of wires along the side of the boat. When that tube is full, if you are planning on upgrading at all, routing new cables from the batteries to the bow is like trying to fit a pen through a needle hole. By taking everything above into consideration, you should have a better idea of how much the boat will actually cost you in the long term.