Babies BRBs can do well in something as simple as a plastic storage tub. Adult Brazilian Rainbow Boas need about 4-6 square feet of floor space in their cage. Although some Baby BRBs enjoy climbing, tall cages aren't necessary. The most important consideration is to limit ventilation to easily maintain the high humidity required for this species. That combined with a large water bowl and a damp hide box will keep Brazilian Rainbow Boas healthy and happy. I hope this answers your question.
Here is a link to a Brazilian Rainbow Boa Care Sheet
and Brazilian Rainbow Boa Frequently Asked Questions