Hi
There are some great threads on viv setups here, and soo many options I couldn't possibly list them all. You could also read a few care sheets and collect ideas from those.
I use one of these plastic shoeboxes/sweaterboxes/geodes (I really don't know what the correct term is!) to keep my big boy in when I clean out the vivarium.
When he was a baby I actually kept this inside the full-size viv, complete with its own hides and whathaveyou, with the little 'door' in the top left open. That way I could more easily ensure the conditions were right and he could also decide for himself when he was 'ready' to explore his giant home. I noticed after a few months he rarely used it any more, so removed it and put more decorative items in its place.
That might be an idea you could use too, seeing as you will need to buy a suitably-sized vivarium eventually. [I do have an extremely confident snake though - he was out parolling the viv on the third day, and it must seem massive to a baby snake!]
Oh, and they are very light, depending on what you put inside them in of course.
Heating is a worry because UTHs, which many of us swear by, can get very hot indeed under the substrate and as we all know, snakes love to burrow or hide underneath it.
You could use a light if you decide to keep it just in the plastic box to start with. Have a word with a reputable store owner and see what they recommend for reaching optimum temperatures without decreasing the humidity too much.
There really are so many options... If I were you, I'd set the enclosure (or initial enclosure) up completely, take temperature readings in various places, including underneath the substrate if you use a UTH. When it's all ok, then introduce snake. Others will be along soon I'm sure to indicate when they move their young snakes into larger vivariums.
And just in case you weren't aware, heat rocks are a big no-no.
(Whew)