Hi there, we've looked after Chinchillas, for friends many years ago, when I was in my teens. Would you just be fostering them or giving them a forever home because something to be aware of is that they can live upto 15 years of age.
As you know they are largish and quite active small animals so will need a large cage. We had ones in cages around 4ft x 4ft. They also like to have company, for some reason they don't like being alone, you can keep them in same sex groups and mixed groups but if there are males in with the group they will mate, so best to have same sex groups. They like interacting with people once they are confident with you and tame enough and like to come out the cage for exercise, so you'll need to make extra time to spend with them. They need plenty of things to do because they can get bored.
They need a diet high in fibre and protein and also like Hay, they will also eat carrots and other types of vegetables but not too much, they also like raisins, sultanas, dried fruits etc. Fresh water should be given to them daily. Nothing high in fat should be given to them like nuts, it could cause stomach problems!!
Like hammies they also love their sandbaths, so a good deep supply of sand should be given to them at least once a day, do not keep the sand in their cage as they will use it as a toilet.
Anyway that's my little knowledge of Chinchillas, just to give you an idea, i'm sure there might be someone on here that might be able to offer some more in depth advice, however i'm sure if you Google Chinchillas, you'll come up with some good information.
I'd love some Chins but just don't have the room at the mo!!