are you really sure you want a fennec fox? I haven't herd of ANY type of domestication efforts for that species... sure they look cute, but when i looked into their diet and habitat, it said (and I quote the National Geographic website)
"These foxes dwell in small communities, each inhabited by perhaps ten individuals. Like other canids, male fennecs mark their territory with urine and become aggressive competitors when mating season arrives each year."
it also says that they live in underground burrows, and "Fennec foxes are opportunistic eaters. They forage for plants but also eat rodents, eggs, reptiles, and insects." (you did mention that you have other pets)
they also mentioned
"These foxes are cream-colored with black-tipped tails. Their adorable appearance makes them favorites of the captive pet trade"
the whole under ground burrow/community dweller desert habitat would in and of itself be a challenge to replicate, the marking sounds like it would be a definite hassle, and the fact that this species is involved at all with captive pet trade... I'm not saying you haven't done your research, but i definitely urge you to do some more if you haven't more than one or two information sources, from what i see, keeping this kind of animal would take a lot more commitment, (not to mention time effort and money) to take care of, a whole nother level in comparison to chinchillas (most people concider chins to be a high maintenance pet) i just wish for ANY (I'm not targeting you here) person considering taking on a new exotic pet (or any pet for that matter) do ample research first, so as to know just what they're getting into... and for its involvement with captive pet trade*, i would also look into the legality of the method you may or may not eventually choose to obtain one or more of these animals, such as where they come from, importation laws, as well as state laws about the keeping of exotics, you may be required to spay/neuter any animals you obtain, as well as possibly regester them with the state
*-(someone please correct me if i am wrong, but I believe that this is the term used for when native peoples capture wild animals for sale as pets in other countries, and is often involved with black market retail)