A few questions (not that I need answers to, just for you to consider):
Are you renting where you live? or do you own your own place? Consider where you'll be living, even if local laws allow them, pets like these aren't usually welcomed
by landlords.
When your snake gets huge, will you have reliable & snake-competent friends or family around to help you with it...because for safety, you need one or more others
around for handling big constrictors. We don't want to read about you in the paper, because that's what gets more laws passed against keeping them.
Will your budget support not just the price of the snake & the giant enclosure, but also the food, the heat (thermostat etc) and money set aside for exotic vet bills.
Not all snakes have the same personality...what will happen if yours evolves differently than you planned for? That's an awful lot of snake, & not what I'd recommend
as a pet, especially your first one that's that large.
You ask about where to get enclosures: many ppl build their own, or you could get "handyman" help? I'm sure others here may have more suggestions too...a BCI was
more than big enough for me.