What should you know about chinchillas before I buy them?

You should know,

Its diet, foods that are okay for it and foods that arent.

What type of caging it should have. (Tall)

What is grooming needs are

If it can live with other animals or not.

Lifespan

Cage cleaning

You should be able to find all these answers at any pet store.

ALWAYS be sure you buy your pet from a good pet store.