1. Ferrets are NOT legal in CA, but Chinchillas are.
2 Despite what the "experts" have told you, a ferret IS a kind of weasel, if the term "weasel" is used to mean any member of the Mustilidae family. The domesticated ferret and the Long-Tailed Weasel, or Stoat, both belong to the same genus, Mustella, though they are of different species. A ferret is a weasel in the same way that German Shepherd can be called a canine, along with wolves and coyotes.
3. A ferret of the species that are kept and bred as pets is a totally DOMESTICATED animal, one that has been selectively bred for gentle and tractable temperament for thousands of generations, going all the way back to ancient Greek and Roman times. In contrast, other weasels are WILD animals, that have NOT been artificially selected for gentle temperaments by humans, but have instead been imbued by natural selection in the wild to be nervous, very active and suspicious of anything unusual, and to view any larger animal as a potential predator, humans included. While wild animals can often be "tamed" through the process of imprinting from birth by being hand-raised by humans, they are far from domesticated, and still subject to their natural instincts. The weasels I've been priviledged to observe in the wild were VERY quick, nervous, high-strung animals, much more so than the most hyper ferret!
4. I've never kept Chinchilllas, so I can't answer anything about their lifespans. I DID breed and show ferrets for several years though. Most ferrets, unaltered, would live for an average of 8-12 years. The same goes for ferrets that I had altered(neutered or spayed)after they reached adulthood. In contrast, most of the pet trade ferrets that are altered while still very young kits, often before their eyes open, seldom live more than four-five years, and this is from personal experience. Wild members of the genus Mustella, with the exception of mink that are raised for their furs on fur farms(and needless to say, THOSE have a very short lifespan)are very seldom kept in captivity due to their nervous, high-strung nature, but I doubt that they live as long as a ferret due to stress, and a weasel in the wild would be very fortunate to survive its first two-three years, due to disease, predation, trapping and lack of adequate food.