check the condition of the carpet, try to get a feeing of the floorboards. Stand in the boat and if you feel any soft spots, if the floor needs changing.
check the wiring, if it looks neat, thats good, if it looks all spliced, then be aware.
check the bilge pump and listen weather it turns on smoothly and quietly and also the pump for live well.
check the electronics if they operate and the holders are not cracked.
check the lighting and the trolling motor if there is one. make sure the troller works.
check the age of the batteries for starting and trolling
check the trailer tires if they are worn and see if the trailer is equipped with bearing buddies. does it have a spare?
check the prop look for bent and dents and unscrew the lower unit gear oil screw to check condition of the oil and for metal bits on the screw.
most the top issues are bargaining items and not real deal breakers and can be fixed or replaced for reasonable amounts depending if yu can do it yourself.
the one thing that is most important is to have the motor compression checked. if compression varies by more than 10%from one cylinder to another or there is no compression, the motor will need major expensive work.