If I was going to run a Charter Boat in the Sound I wouldn't consider anything under 24' and with a deep vee hull. Most people going on charters want to catch fish but they also want comfort. So something with a hardtop for them to get out of the weather. We all know the grey days that happen. I would also buy a quality boat that doesn't require a ton of maintenance.
I guess my biggest question though is why you want to charter in Puget Sound. I have known a ton of charter skippers that have went out of business in the sound or moved to other more cash productive waters. Only a few can even make a partial living doing it anymore. Most of them have other jobs to supplement. The seasons are too unpredictable and catch rates limited. If money isn't an issue then more power to you. I can't think of a better place to be than a boat on the Sound.