like lgray said, i would advise on a ball python before a boa, boa's are nice and can be just as docile, but they are more prone to have snappier individuals, you should also consider corn or king snakes, their both super easy to care for and really docile, although they can be pretty fast, but would be better if you want to watch roam around a tank, theyre both pretty active during day hours, BP's tend to only come out towards dusk or night time. any of these are great begginers though, but just remeber that boas get about 8ft or so, and have been recorded up to 12, although thats usually with power feeding