I agree with rick, however not even alligator snapper get 500 lbs. the record is like 319 pounds, but I would not expect a weight that much until it is passed on to your grandkids.lol. You don't really have to get a tank liek an aquarium. you can get a huge stock tank for like $150. and that woudl keep a common for quite a long time. snappers have quite an appetite. My parents were once like that, about the dangerous snappers. They are not dangerous unless you goof off with them or show off or something. if you take precautions you won't get bit. If you would happen to get bit, it is your fault and always remember that. I have had no problems with any of mine, and I have had them up to nearly 50lbs, and aggro but never even came close to getting bit. Do not pick themup by the tail, if you did not alreayd know. Just keep the water clean and at the right temps. I find snappers more interesting, but that is my opinion though. a racer would be the least expensive, but it is much betetr to give them a somewhat larger enclosure than you would a rat, as they are very active and that is mostly what causes the nose rubbing. I don't think a large w/c racer would be a good idea for a biginner, Go with a baby. Either way, if you go with snapper or racer, just know what you are doign first and keep the responsibility. you should sit down and discuss it with your parents. oh and if you pick snapper, you might even go with alliagtor snapper, as they are slower growers, but get bigger int he end. They are slower and have shorter necks that can't reach you as well as a common. Alligator snappign turtles is like on my top 3 list of favorite animals,a nd are just sooooooo interesting. I have seen you ont he snapper forum and I know you have good intentions and have done your research, btu it is your decision in the end, not ours.
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Justin