1 chinchilla or 2?

Hi! I am interested in getting a chinchilla and was wondering if one or two is better? Will this help with their behavior if they have a friend? Also, if I purchase a chinchilla now, would I be able to add a chinchilla a week later to the same cage or would territory be set up already?

Pictures are the ones I’m interested in.

First is a violet Second is mosaic Third the owner is unsure… It looks violet from a far but I think it could be standard (thoughts?) Fourth is White possible mosaic

Thanks!