Rich,

Anyone who offers you a guarantee is full of shit.
The best anyone can offer is targeted traffic, and their best efforts to work with you to make it work.

My advice is to start very small and find out what works for your site one opportunity at a time. 10,000 clicks at ten cents per (for example) is still a thousand dollars. You know what your average conversion rate is for traffic to your site -so you know how many of those clicks have to buy to make up your money and how likely that is.

Obviously i sell adspace on QueerClick, no hidden agenda there. But I'll NEVER lock anyone into a long contract. My traffic doesn't work for all products, not everything sells. I've been shocked on occasion by what did and didn't sell. What I can do, is try to minimize my clients' initial risk so that if it works we all cheer and if it doesn't we can part ways amicably.