Like the others said about checking the outdrive,make sure you have someone check that! Also look at the exhaust bellows, shift cable, and the trim angle sensors. Those parts are not too expensive to buy, but the labor is a real killer on those.
Make sure you test it at a lake. Things may look good while it is on the trailer, when you add water the game changes.
Do a compression test on the engine, look for any sign of water in the oil. People have a habit of not winterizing, then getting a cracked block. They forget to tell you about it.
My .02