That is a common columbian boa constrictor (BCI). He is not a true Red-Tail Boa (BCC). The true red-tail boas are unmistakable once you've seen one - their tails are blood red. This one is not an anery either. Anerythristic boas have reduced red pigment and will be all grey and black. There is red pigmentation on this boa's tail - he has normal coloration for a BCI.

Normal BCI's can be found on fauna classified and kingsnake for $30-40. While $100 is not necessarily a bad deal if you NEED the tank and all the equipment that goes with it, it is rather high if you don't. If that's the case, then you may want to think twice about this one. These boas are quite common and if you're just wanting a pet with no special genetics involved, you can find one quite easily for about $30.

There's nothing wrong with keeping your snake in a tank instead of a tub, if you want to use this particular set-up. Humidity might be an issue, but there are ways around that. And you might not have to get a bigger tank as soon as you think. A boa this size will be quite comfortable in that size tank for about another year, then you'll have to upgrade. This deal might be a good way to go about it now and slowly purchase your tub and supplies for that once he is closer to outgrowing the tank.

BUT I have to admit that I'd dubious about this being a male central american boa. Simply because most people selling on craig's list are simply not that well informed (I'm just making a generalization - please no one take offense!). And are you SURE this is a male? If the person selling it is 100% sure and is 100% honest, ok. If this is a male BCI, you're looking at an adult of 6-7 feet. But he turns out to be a she, then she could be 9 feet or more! Are you prepared for that? I would wonder about locality and sex coming from an ad off craig's list. Most reputable and knowledgable sellers are going to use fauna or kingsnake.

Just my 2 cents and food for thought......