Personaly,the only two things I would be concerned about are the condition of the hull and the engine/gearbox. Things like insulation,wiring you have to relate to price. If the boat is cheap enough and you have checked secondary items(which are still quite expensive)like cooker,fridge,water heater,inverter-charger then you have to make a judgement. Our last boat was bought on a whim and suited us well for 11 years .In the end ,condition of the bottom plate(6mm) pushed us to selling up.(The new purchaser was aware of the problem) In retrospect,I wish we had spent a bit more on a newer boat with a 10mm bottom plate. On length ,going down hill on a boat the max size for any given lock,you may get very wet. There are some very leaky loch gates out there.