Rankpay.com offers a unique off-site SEO service. You pay only for what they manage to rank you for. It works quite simple - you enter a site and add few keywords. and based on their algorithm they calculate how hard is it to rank your site for these keywords. You enter your credit card number and do not pay anything immediately. Only after certain rankings are achieved you start paying monthly sum according to the plan you were presented at the beginning. No rankings - no payment.