I have been in RC for several years now. I have raced a few times but really didn't enjoy it that much. Everyone seemed too up tight to me. I even saw a few dudes almost come to blows. All I could think is what a bunch of babies. I have just as much time and money tied up in this hobby as they did if not more, I am a collector. And I never get that uptight. I also did not like to be rushed to make repairs or get to the track on time. I just want to have fun. I like to upgrade my RC's and learn how that affects them and measure the speed with a GPS. It is people like that, that are runing regular sports for their kids, making them to be too competitive and not letting them have fun. I am lucky and have time to go to the track or lake when everyone else is at work and no one is racing and just have fun. I just got into RC Boating about 6 months ago and I am having a blast. It would be nice to find someone else in my area to kinda race around with. But sorry I am not in AZ.
To answer the other question. The hobby is pretty expensive. You can buy some cheap stuff or get deals on Ebay, but the good deals are hard to find and before long 10 guys are bidding on it and its not such a good deal anymore.
Just take the boat you have, get some batteries from Cheapbatterypacks.com and a charger and go have some fun.