Deb: I've raised AKC registered beagles for 20 years. I hunted cold blooded dogs for about 5 years before I got into the registered hounds. I'm not trying to discourage you, but a purebread has some advantages. There are lots of pups raised every year, only a few good ones, and very few great ones. Pure breads at least have a history, and knowledge of the blood line is important. Pure bread hounds are more consistant in quality. I've seen some very good cold blooded hounds as well, but when bread back to another hound, the consistancy isn't as close. What I mean is that speed and style can vary greatly from individual to individual much more so with cold blooded hounds than with registered stock.
During the 60's the old guys slowed AKC beagles down to the point they really didn't suit the average hunter. During the 70's, the gundog movement started, by breeding the faster hounds that were not suitable for slow brace trials.
In my perticular case, I have personally watched every hound in my blood line for the last 4 generations.
With a cold blooded dog, that has no history, it is very hard to predict if the dog is going to make a hunter, and after much time and effort has been expended, it is discouraging. Not to say that you can't get a bad purebreads out of great stock, because you can and will, but the odds are higher that the hound will have some quality. One thing for certain, it cost the same to feed a good one as a bad one.
I would recommend that you buy as good a bread pup as you can find from a reputable breeder in your area. Speeds and styles vary by area, and the long time hunter breeder in your area will have bread a hound to run in the conditions for your area. While a pup will take a little longer to get where you want it, you won't have to worry about someone dumping an undesirable hound on you. Also with a pup, you have the same odds as anyone else of getting a good one.
I would highly suggest attending an AKC, UKC, or AHRA field event in your area and watch. Pick a pup from hounds you like, but first, learn what you like and you won't get burned.
I'm pretty sure you can download a rule book from AKC.org which describes desirable qualities and faults, and this is a good place to start.