Instead of looking for a cheap Vision cage that won't be a proper cage, why not look at the ideas for building the caging out of a big water trough? It won't take up TOO much space, it will allow for proper dirt and substrate so it can dig and have proper humidity and will be sturdy enough to last for many years for other pets, when the monitor outgrows it.

A typical water trough cage might keep it until the year is up when you say you'll be moving and building the outside enclosure.

Because tanks are terrible, visions are terrible. Monitors are tough and will refuse to show any issues, but they can die from issues they end up with from being kept poorly to begin with. Kind of like if someone keeps a pet without enough water for a long time, and then a good keeper takes it and makes sure it has plenty of water all the time. It can still end up dying from kidney issues that developed when it didn't get what it needed, even though at the time of death, it was being cared for properly. "Making do" with a monitor lizard can end up killing it.