I would go with a 21 to 23ft open bow boat like seagar said. If you are going to be trailering it from home to the water, then an open bow is the way to go in my opinion. That little cuddy cabin ends up being used as a storage closet in most cases, so its kind of a waste of valuable passenger room.
My first boat was a 1968 17ft Glastron bowrider (85hp outboard), got it for near nothing but I overhauled the whole thing down to the beams in the hull. i trailer it around to lakes in the area great for day trips. But now I have my 1994 Maxum 2700SCR (7.4L/Bravo 2 Inboard/Outoutboard)on a mooring in the sound, which is like night and day. Much more maintenance involved with the salt water and leaving it on a mooring.
Definitely do a compression test like phillbo said, it makes sure that the engine is running at correct levels (psi)
look into outboards as opposed to inboard/outboards to see what fits you best. 21ft bowriders are all over the place, im sure you can find a good deal on one somewhere.
Hope that helps,