Check everything... I didn't and it easily cost me another 1500.00 to get it close to where I want the boat to be. Simple things like pumps, lights, switches and not knowing the trailer bunks had the carriage bolts installed on the outside of the carpet and had rusted and rubbed holes in the gel coat and fiberglass on the hull. If there is a switch on the console it should turn something on, make sure it does.
Put the boat on the water, runs the live wells. Spend an hour on the water and see if the hull takes on any water. Do a simple compression test. Open every box and look in them. Check the transom out too. Spin the prop, is it the prop beat up, does it wobble? I looked at one boat and almost missed that the skeg was bowed, looked closer at the lower unit and would bet it needed replaced because he had hit something pretty hard.
That's all that comes to mind.