Maryrrf is right on to tell you not to count on ticket sales. That's a good way to go bust in a hurry. Three things pay for a festival: program advertising, grant money and vendor booth fees.
Be nice to your vendors, work with them to meet their needs and make them want to come back.
Get onto working for grants and sponsorships NOW -- contact your state Arts Commission and ask for guidance, and hie thee to the library to ask for their books of Foundations. This one is a slow and tedious jump-through-the-hoops job, but the payoffs can be huge. Lots of "how to" stuff on the web and in the library, and a cover letter to most foundations will result in an answer of their requirements for applications.
Set your program advertising as low as you can, to sell more ads -- when you're a big noise, you can raise them a little "to cover rising costs" (which, alas, will be true enough) and see if you have some local organizations, especially with kids in them, who will sell ads for a split on the take. People will buy ads from kids who will turn down adults flat. Dance schools, music schools, etc. always need money for those expensive outfits and accoutrements. I could do a whole book on program ad sales. There's real bucks to be had here, but you have to go about it with an eye for the local "main chance."
PM me, if you like, and I'll give you my e-mail address as soon as I can and will send you info. We're less than two months from our festival here and I'm up to my (blub, blub, blub...)