Caging
Caging depends a lot on the specific animals requirements. In general the bigger the better. And you do not want any cages with a wire floor.
Rodents
Small rodents, mice, hamsters, gerbils and similar can be kept in glass aquaria with well fitting screen covers. Hamsters and gerbils can also be kept in wire and plastic cages, though all rodents chew and may make an escape from an all plastic cage. Mice should not be kept in wire cages as they can squeeze through very small gaps.
Most of the smaller rodents also do well with exercise wheels though you should stick to the mesh or plastic ones to present foot and tail injuries. Also buy a larger wheel than you think they need to avoid spinal problems due to an unnatural running angle.
Larger rodents are often housed in larger wire cages. For rats and chinchillas this is ideal. Chinchillas need lots of airflow. Guinea pigs are normally housed in wire cages with plastic tub bottoms. They chew, but not quite as much as their smaller relatives. As guinea pigs are not good climbers and only mediocre jumpers they can be kept in pens with no cover as well if you have no other animals that might try to get to them.
Rabbits need again the largest cage you can afford, or to have lots of outside the cage time. Avoid the wire bottomed cages that were popular for a time. They are really only for rabbits that were being raised for meat. If you're going to eat something in less than a year you don't care that you're screwing up it's legs by making it live on wire.
Ferrets
Expect to give your ferrets plenty of time out of the cage, but get the largest one you can afford. Ferret cages are often designed to go high rather than wide. If the cage is quite high, make sure to fill open space with hammocks and other hanging items to help prevent a nasty fall. Wire does not make good shelves or ramps, but most cages come with wire. Cover these with something to keep feet and legs safe.
Maintenance
Any cage should be cleaned at minimum weekly. Some animals can be litter box trained and that should be changed more frequently to keep them interested in using it. Food should be checked and refreshed daily, as should water.
Inspect any cage you have as often as possible, as animals may be chewing holes at night that you won't notice till you no longer have a hamster. Assume any animal can get out a hole as big as its head.