Wordpress Plugin Creation

I'm looking to have a Wordpress Plugin made. These are some of the features I'm looking to have as part of the plugin: The plugin is a paypal buy button and opt-in form. Meaning that whoever buys something using this button, their paypal e-mail is collected and added to an Autoresponder List of the choosing of whoever is using the plugin on their page. This means the plugin has a 2 part function: 1) used to make purchases 2) used to obtain e-mails I want this plugin to replace ordinary buy buttons, but I also want the button to side scroll along with the viewer, this way the buy button always stays on the page, wherever the operator decides to have it appear. I would also like the option built in, into the button, (since it's using both paypal and e-mail) to have a feature where you could create your own Joint Venture. This means that by using the plugin, people can subscribe, and receive a unique link that keeps track of Commissions, Clicks, and other stats, allowing the plugin user to have Affiliates join in on their projects without the use of a 3rd Party Site. I'm not sure how much this type of job is worth, as I am a first timer in this sort of thing. Please notify me around how much this will cost and how long it will take to have developed.