Hey Downriggin, good luck on your future endeavors I hope the charter thing works out for you, I've actually thought about the same thing but I must admit, I've been spoiled by my years in Alaska, I don't think I would have the patience to spend alot of time on the Sound, that, and its hard to give up the gig I've got going up there, someone elses boat, gas, gear and room & board to boot.

Anyways, if I were to do it, I would run a 24/25 ft. boat, (4 clients will make you more $ then 3), and 22 ft boats get crowded fast with 5 men on board (I actually fished 4 out of a 21 ft Glasply for a couple years, not fun) don't cut corners on the power plant either, I've run Yamaha-Merc-Johnson outboards, a 454 gas engine and currently a Volvo turbo-diesel, if I were out fitting a boat the diesel would be a no-brainer, a hell of a lot more reliable and 1/2 the fuel consumption.
Another consideration is insurance, I've seen alot of strange things happen, hooks through various body parts, a tuffline amputated finger, stitches in the head after slipping on halibut slime, there's more but you get the point.
Chartering is brutal on equipment, I can't even guess how many rods I'll go through in a season, and reels, if you don't know how to rebuild now you'll probably learn soon after starting up. Then there's the terminal gear, get to know some reps. that will help a bit.
If you are not Coast Guard licensed you'll need to get an O.U.P.V. or 6 pack license, with your time in the Navy sea-time isn't a problem, the test takes some studying for but not that big a deal.
Well, I hope this doesn't discourage you to much but there is alot to consider when taking passengers for hire out on the salt.
1 last thing you might want to think about if your serious about chartering is spending summers up north, I know I could not make half the money here in the summer that I will make up north from Memorial Day to Labor Day, and there are alot more and bigger fish.
I hope this helps a little.