Welcome to the group Countryboy88. We love to see new members anytime. Youll find there is no one size fits all boat. They are all fun and they will all sink, and they are all expensive.
I see on airboat trader some smaller boats with 90 HP GPU and some with 150 GPU motors. I started my kid off in a 90 GPU in a 10'x6.5' deckover West Palm style and it served its purpose as a trainer. He learned its quirks and how to handle it. By the time he was ready to move up he was running like a pro.
Generally speaking big HP and big weight arent the ticket for a beginner, but if ya find the right deal anything can work if you have a level head, learn from the right people and take it serious.
You aught check out
http://www.airboattrader.com/
Theres stuff there you can get for under or around $5,000 that if you tear it up it wont kill your budget. Especially if you are handy with tools and can do a lot of the work yourself.
Make sure that you have all the necessities of life wired first though. Airboats are fun but dont neglect family, transportaion, housing or food to get one. We dont know your finances so all we can offer is advice and cautions. An airboat at the wrong time can ruin your life, at the tight time it can add a tremendous amount to life.
If you live close to any of us you might get in contact and go for a ride and such, get to know some airboaters before setting out on it all alone. Lots of good folks here willing to help.
Scotty