Hopefully you can post a pic of your new pet so we can confirm it is in fact an amarilli.
Acquiring an amarilli for $10, or even $100 (if that was a misprint) is unheard of.
Amarilli are much more rare than your typical bci, such as the common colombian boa .
They are not for the novice keeper, as they do require a higher level of knowledge and/or experience. They will pose more of a challange to breed than other boas, however this is by no means an attempt to persuade you otherwise.
Some of the less expensive Bolivian Amarilli can be seen as pets, but other more expensive variety's, such as the South Brazilian locale, can be much higher in value and more difficult to find. Because of this, they are not common pets, and there tends to be fewer breeders working with these magnificent animals.
A few top breeders that can be found here on the forum are Barry Miller and Phillip Notoro - Bill Cagle also carries many of these animals produced by Barry and others such as the great Lloyd Lemke.
For starters, feed less than a common boa, and maintain the humidity a bit higher.
You should be able to find much more info here...
One site I believe can be helpful is Gus's site - RioBravoReptiles
Hope this helps - take care - Joe
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Thanks and take care - Joe Rollo
'Tis not the stongest of the species that will eventually survive, nor the most intelligent, but the one most responsive to change' Charles Darwin