Buying that boat sounds like a pretty good plan, that will definently save you money on all the accessories. and allow you to focus more on the hull. Try searching for boat salvage yards/ hurricane boats. I know there are some websites that sell flooded/damaged boats at dirt cheap that would make a good parts boat.
attached is a pic of the boat I built from its first launch,It is the glen-l flying saucer design. Wasnt registered/totally finished yet. As you can tell I was pretty happy with it, so happy that I forgot to take the bumpers up, a little sloppy seamanship on my part 
since the first pic I added a small wind-shield, more for looks than function. I will try and dig up a newer pic today sometime and post it.
I also will try and get a picture of one of the racing boats from the grand Island boat show. they really do have motors over 250 HP in them,
quite the thing to see first hand.
The Rocket looks like a good deal, the step in the hull might be a challenge to get right, but nothing impossible. the prop on shaft would be much easier than the v-drive. the boat builders forum on Glen-l will provide you with a lot of answers to your questions. the people on there love to help out when they can. One thing I can tell you is that you will have a blast building it.