i don't know if i would call it a day job, but i own a swim school, intotheswim.com
. i started it because when ever i didn't have a tour i always taught swimming. now it runs without me for the most part. i tour whenever i want and fortunately it is successful enough i can be more selective on what gigs/tours i want to do. to be honest, you'll find a lot of "pro" musicians are doing similar things.