I have never owned a boat before but am considering buying a used rig in the near future. I'm looking for a shallow water bay/flats boat. I've been scouring craigslist and other sites and there are a $hit-ton of boats and styles out there.
The ones that appeal to me are styles like Blue Wave, Kenner, Carolina Skiff, and some of the entry lvl Majeks. I do a lot of fly fishing so something that I has a forward and rear casting deck would be nice. Ideally I would like something in the 16-21ft range.
I've seen prices ranging from $3k up to about $13k on similarly equipped boats depending on year and motor size.
What are some things to look for when purchasing a solid used boat?

If you are looking at a tunnel style boat, skip the Bluewave. Trust me on this one it comes from experience. The Carolina Skiff is a kohuna busting bugger, but will float in spit. If you can find a Majek or Kenner, look closely at the transums and where the transum meets the floor. You may find a crack, Gelcoat cracking is ok but look a little deeper for fiberglass cracking. Do not get a bay boat mixed up with a flats boat. Flats boat have to get up in 2foot or less water. Bay boats don't. If someone tells you that their non tunneled hull runs in 6 inches of water, he's full of hockey puck. He will be blowing more mud than water. Don't be afraid to test drive the boat, A lot of the so-called flats boats are self steering. Meaning if you hit another boats wave the boat will self-steer down the on coming wake. I'll tell you, that will get your shorts in a twist. Especially if your 10 feet off the side of a canal. Stomp around every inch of the floor, a lot of boats don't install their consoles in a bed of sealant and the screws become loose where water can enter. That causes rot. Also on a total composit hull, Look closely at the water line across the transum. If it is leaning in the water it could be a good indication of water logged foam floation. Which brings me to this....There are a few boats being made and sold that do not belong to the NMMA. No NMMA tag, walk away. There are two reasons for not belonging to NMMA, one they cannot pass the testing, two; it's a non stable company that may or may not be around tomorrow if something goes wrong with the hull.
Of course I could go on forever about flats boats or bay boats but I'll keep it short and try not to over emphise my opinions.

Thanks for the reply Mike.
What I'm really looking at is something that will get me up into the flats down in the LLM and the marshes closer to home near Galveston. Nothing fancy, just a good, solid little boat to fish out of.

This link should get you started in the right direction, lots of good advice all in 1 place, especially if you haven't been thru the looking and buying process before.

http://www.bassboatcentral.com/buyingusedboat.htm