To the left is an example of a spacious cage set up for two Chinchillas. The cage pictured here is a Ferret Nation 182 single unit. ( click photo for shopping option ).
This unit is large enough for 3-4 Chinchillas. The bar spacing is 1" wide making it safe for adult chinchillas, but chinchillas 3 months old and younger can easily get stuck in the bars, or worse escape their cage and get injured. So it's best to get a cage with the right bar spacing and height for your pet.
There are other cages on the market that will work just as well.
Chinchilla Breeders use Breeding runs to safely house their animals. A breeding run is generally smaller than a pet chinchilla's cage. The breeder chinchilla's cage will be somewhere around 15"W x 24"D x 15"H. Runs will have 3 or more small cages, and a long tunnel like cage in the back. The cages will house the females, and there is a hole in each cage that only the male can go through. His tunnel in the back gives him access to each cage.
The females cannot enter the tunnel because they wear a light weight breeding collar that prevents them from fitting. This is for the safety of the female, because without the collar she may wander into another female's cage and because of hormones and territory issues, they will fight. Fighting can result in injury, loss of pregnancy, and death. The small cages and collars are for their safety.
A Chinchilla in breeding will also not have most of the luxury items pet chinchillas have ( multiple ledges, tunnels, houses, swings, etc. ) because those items can be a health risk to the kits growing inside. If a Chinchilla misses a landing, falls, or hits one of these items it can kill a growing kit.
Though they don't have the luxury items, they are still fed a healthy diet, given ample chew items, and are always offered hay.