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[Fennwick]

im gonna have to disagree with Naxx(no offence). i think the easiest way to build an enclosure is to convert a piece of furniture. cut a couple of holes and use sink strainers for cheap, nice looking ventilation. make sure its escape proof. dont under estimate their ability to get out.
and im gonna agree with some of the other guys - get a carpet python hatchling. i reckon coastal carpets make a great first snake(notice i said "first"). it'll start out small, but will grow to a beautiful, gentle giant. they're also very hardy and will easily handle newbies mistakes.
just persevere with your parents. i can guarantee after a few months with your snake, they'll turn into snake lovers too.
before you go ahead and get it, search this site and ask lots of questions.
good luck.