For what you want to do I'd say a 21 to 25+- CC on a trailer with a 4 stroke outboard. Your problem is going to be lack of use. Worst thing you can do with any boat is not use it. Unless you can store it in a temp controlled environment. Water condensates in the fuel tank fouling the fuel. It's less of a problem if you keep the tanks full all the time, and even less if you install seperators. A good set of water seperators are worth their weight in gold. They do need to be checked and cleaned regularly. It's a bit more expensive but using premium fuel helps as well.
Next will be your electrical system. Every connection should be soldered. I also epoxy and shrinkwrap every splice, crimp, or tap. Never had a problem. Terminations, plugs, and switches are a different story. The best advise I ever got was don't go cheap. Costs you far more in the long run. I use Military grade switches for everything. As often as stock switches go bad, you'll want to keep some on hand. Here's a link to what I use. http://www.apem.com/military.html
You want to coat your termanal/fuse board with a good water displacement product. They make several for this purpose & most any will do fine. WD40 is OK but not what I would use. Mercury Marine makes an excellent product for this, I use it on both the connector and the termination. Then screw it down and wipe off the excess. Again, never had a problem.
For motor and impeller maintence, (Lower end) There's a bit more you can do than just rinsing off the lower unit. Take a 30 galon plastic garbage can, with the boat on the trailer lower the motor to the run position. Place the GC so the lower unit in in the GC clearing the prop. Pour 2 gallons of plain white vinegar in the GC and fill with water about 3/4 full. Run the motor in gear at idle or just above for 10 min. let sit for an hour and repeat. Do this 2 or 3 times. The vinegar will disolve the salt in the cooling system without damaging anything. You'll never overheat.
Last is trailer maint. If you trailer, you need to know that you never want to submerge hot berrings in water. Instead get to the ramp early and let em sit for for a bit. Also helps to have dust caps on the wheel bearings with grease fittings. Give em a pump of grease every few times you use it. head's off allot of problems. Trailer lights, you want sealed unit's if it dosen't have em already.
If you wait for things to break you'll be working on your boat far more often than if you prevent problem's in the first place. I've owned and worked on dozens of boats over the years. I can tell you first hand the saying "an ounce of prevention is worth a pound of cure" was never truer than with a boat. Just be sure to change filters and fluids as reccommended, and follow the advise above (You can do everything in an afternoon on a small boat on a trailer) and you'll spend most of your time enjoying it. Good luck!
PS I agree with Cuda about Bayliners, and Hydrosports have a bad habit of dolphining.