Very difficult and actually impossible if you have no traffic. As long as you have good targeted traffic, then making money shouldn't be to difficult. You also need to target your ads well and optimize them well into your site.
I'd say if you're going to be able to make money with ringtones then you should be able to make even more money with another product with the same amount of effort. It's a real tough market like john269 sez. donrock
Sign-up and read Shoemoney's blogs - he's into Ringtones big time... I think it's all about how much money you're willing to put into it tho as the competition is huge... There's still money to be made if you can come up with a different angle.