I bought an 18' pontoon with a 25 hp 4 stroke. It does 12 mph. It mostly stays on one lake.
I love the thing. Great to recreational fish from, cruising, bimini top for shade, comfy, can carry lots of people. I have a down rigger mounted on it too.
18' would be the minimum size, docking is easy. I would buy one with a trailer (I did). A carpet floor gets dirty and moldy. A net helps landing fish because you are pretty high off the water.