That's a really good question. If you live in an area that has a lot of venues within reasonable driving distance, then all you need is a day job of nearly any kind, preferably with weekends off.
It will be hard to find any kind of steady job that doesn't require you to be there on time every day. Few employers are going to be fine with you going on tour periodically. If you do seasonal work, then you may be able to arrange your travel after the seasonal work ends.
Working for big music stores MAY be an option, since most of the employees are musicians. You can even get discounts on amps, mics, and instruments. But when you leave, they will probably fill your spot. Also, EVERYBODY wants Friday and Saturday off, so there may be pressure to get you to be the one that has to stay and sell guitar strings and drumsticks to the local players on the weekends.
It's not much fun getting up in the morning only a few hours after getting home from a gig, but it's nice to have gas in the tank and a roof over your head when the rains come. And the rains WILL come. I've made good money both working a straight job and augmented that income with a steady stream of good musical gigs.
I've actually moved across the U.S. to live and work somewhere that I could be much more active in music than my hometown or home state. Some of my buddies from back home moved, too, and got jobs in the new place to keep our musical ties over a lifetime. That's a HUGE undertaking and should not be considered without massive deliberation, but it's very helpful to have the maximum possible paying venues within an or at most, two hour drive. That's why as a young man I moved from the central U.S. to California. Gig Logistics. For me, it was what I had to do. It could have been a disaster, but God has looked out for me all along the way.
I've worked and played for many, many years, and couldn't have made it without either playing or working for the man every night and day. In the times where I was on the road with only music for income, I've been in situations where our van had engine failure, transmission problems, had a wheel come off our equipment trailer, you name it. In those situations you can be a long way from home, and in need of repair money, food money, hotel money. If you don't make it to the gig on time, you're fired. There may not be much room for those unexpected expenses.
Living in an area where the good gigs are within easy reach is a good lifestyle choice if you want to minimize some of the need to travel. Of course the competition for the gigs is much stiffer in those areas. All the better to get really good at what you do. Specialize in a form of music that people are willing to pay money for, unless you are wealthy enough to fund the project out of your pocket. Get really, really good at what you do, if you expect to get paid for it.
All that said, I wouldn't trade the life I've lived for any other that was available to me.
Music is one of the most rewarding jobs I've had the pleasure to have known.
...and I'm still rockin'!