Drupal Coupon Feature

I am looking to have a similar feature to [login to view URL] developed on drupal, I want to be able to setup a auction that runs for a certain period of time, when my users create a content coupon it should allow them to specify a specific number of sales that needs to be meet for the coupon to be valid. Creating the coupon content type is easy and I can do that but the mechanics to around it in a similar fashion to the above mentioned site is required. The user should only be able to specify a specific set of coupons which I should be able to limit. Finally, I want to be able to request people to enter in payment information by me using paypal website payment pro which allows me to keep the user on my site without having to push them over to paypal and accept credit cards. I want to be able to allow people to escrow money, submit money into our paypal account to hold it there to use towards coupons, just like [login to view URL] and http://www.freelancer.com does; its important that the user can see their balance and see what coupons they have bought and paid for and what coupons the bid on but never got. This needs to be on Drupal 6.x