There are so many ways to promote for free!
I have never paid for any type of promotion, just utilized social networks, word of mouth, the forums, anything!
I'm far from quitting my day job(s), but I've done perfectly fine with free promoting. I am only doing this as a hobby, not trying to make it full-time, but I average about 2 sales a day so far, sometimes more...so I'd say try free first!