Our boys live in a 'Critter Nation Style' Cage, it is a 'knock-off' I got secondhand from Trademe.
Our girls live in a 'Ferret Kingdom' Cage, also purchased secondhand on Facebook Marketplace.
The pink bed comes from a dollar store, I cut entries with kitchen scissors and attached to the cage with pipe cleaners. The white 'crate' is from Kmart and is cable tied to the cage.
A seagrass basket upside down makes a good hide for your play/free-roaming area. And cardboard boxes are also a great (not to mention free) option.
Wooden ladders and pumice shelves or lava ledges are available in the bird department of most pet shops and make great cage or free play toys.