$300 for a baby normal BRB is very high. Shipped from a reputable breeder it should run you no more than $200.
For a baby you can use a 28-qt tub with a securely latching lid, like a sterilite latchbox, an under-tank heater that covers 1/2 to 1/3 of the floor space, and a thermostat. Put in an inch of cypress mulch substrate, add a water bowl, and call it done. Keep the mulch damp but not sopping wet and the humidity will be fine. Cypress is recommended because it doesn't mold. When the baby is close to outgrowing that tub you can get a PVC reptile enclosure.
I have snakes and dogs and they are kept well separated; we don't need any vet bills for preventable injuries.