They are very cool boas...even if I am biased.
How docile they are is going to depend on whether they are wild caught or captive bred as well as the age they are when you get them. I've not encountered any captive bred so far that were nippy at all, regardless of age, but my wild caught female tolerates almost no handling what-so-ever - just the absolute necessities of moving her from her cage to a tub for cleaning and back again. My wild caught male has always been very gentle and docile, however he was much younger than the female when he was captured, so that may have something to do with it. He was also a very picky feeder and had to be force fed for almost a year because he refused any and all food offered, despite me trying everything recommended and then some. Generally the captive bred snakes are healthier and already feeding on rodents, though some still prefer geckos, anoles or frogs as prey - especially if they're younger snakes. Most of the Candoia stay under 4-5 feet in length - probably the most common in captivity is the Solomon Island Ground Boa (also known as the Solomon Bevelnosed Boa for those dealers/breeders who've switched to the new name classifications written up by Howard Smith of Colorado University). Male Solomon Island ground boas are typically 2-3 feet in length with females typically reaching 4-5 feet in length. Viper boas are probably the second runner up for Candoia species available, but it is my understanding they are a bit nippier in dispostion (hopefully someone who keeps them will chime in here on them for sure). The price ranges vary - wild caught animals can be had for as little as $20-$30, as can some of the more prevalent natural color phases of captive bred babies, though prices can run anywhere from $40-$125 depending on color and whether it is feeding on rodents. The more attractive and rare the color, the more it will cost...the same goes if the breeder has switched it to rodent prey (more than worth spending the extra money for). For Candoia, the Santa Isabel ground boa (a white phase of the Solomon Island ground boa found exclusively on Santa Isabel island) is probably the most expensive with babies starting at $100 and going up from there. If you've kept other snakes and have good husbandry practices, I'd say these are a good snake to try. But for those with little or no snake keeping experience, I'd recommend they pass on Candoia until they get some experience with a species more forgiving of husbandry errors. They can be difficult feeders, especially the babies, and proper husbandry is a must...temperatures too hot can cause death as they are not forgiving of extreme heat and temperatures too cold can lead to respiratory infections and possible death. Even so, they're a great snake - very unusual in appearance and relatively easy to maintain once you've met their requirements. Hope this answers your questions. I've also provided the link to Jerry Conway's Candoia page which gives a rundown of the different types of Candoia as well as their care requirements.
Welcome to the board!
Raven
Jerry Conway's site