Your city clerk has the local ordinances - ask them about fur farm raised foxes as pets (specify if you are IN or OUT of the city limits).
If they're ok with it, contact your local dept. of natural resources to find out if you need a special permit to have one that's not living on a fur farm (in other words, inside your home). If they're ok with it, or you can get a permit, your next move would be to find a VET trained in wildlife. Not all of them are. A fox would need to have at bare minimum a distemper vaccination and a rabies vaccination.
On the downside, given that foxes are classified as wildlife, if yours would snap at or scratch any human and they report it, your fox would be confiscated and tested for rabies (the testing involves cutting off the head to examine the brain tissue). Even with the rabies vaccine given, your pet would not be allowed to be held in quarantine. States are very strict about that.
I know someone in Wisconsin who had a silver fox. His folks owned a fur farm and each of their kids had a pet fox that was indoor trained. The foxes were VERY shy around strangers though, and would get stressed with loud noises (open mouth panting and wanting to run). Not a good idea to try walking one outdoors. Hounds especially would go nuts when smelling them.