I actually purchased my BP from PetCo as well. I didn't know any better at the time, but then I found this forum and well... let's just say i'd get my snakes elsewhere from now on. The place was clean and the snakes looked healthy and well fed but, it's still a chain pet store. Not alot of T.L.C. there.
For the enclosure, I took a black large plastic container, cut it in half and used it on either side of my 20g long tank. One side I put a heat pad directly under, the other I didn't. To help with temps, I put aluminium foil across 74% of the screen lid.
I live in southwest Florida, so in all honesty it's easy for me to keep the temps and humidity perfect at all times. My enclosure is glass but if you have temp/humidity problems, many people suggest a rubbermaid type tub.
Bought the snake as a hatchling and two years later, my BP is past 3ft 6in as of today and is fat and happy. The snake is a PIG, never had a feeding problem. Sometimes he seems disintristed and will bump his nose against the mice and 'taste' it, but if that happends I just skip that week and next week he's striking at it as soon as the mouse gets within range. Never gone more than 1 week without eating in 2 years.
I feed 5-6 frozen-thawed adult mice every week, once a week. I tried rats a few times but he won't even consider eating them. Hopefully soon he does though because that many mice are a pain in the butt to thaw.
Never weighed the snake. Pretty sure now that he is actually a 'she' because of the time it took to get this size but I never got 'her' sexed so I don't know.
I'm also pretty lucky since i've never been bitten or struck at in the time i've had my snake. Such a gooooood snake! lol.