Enabling blog purchasers to resell same blog at a set price level

How do I accomplish the following scenario?

I would like to sell a blog to my members that enables them to sell the same blog to their personal referrals, and for those referrals to sell it to their referrals, and so on, and so on... at a price that I have predetermined/fixed within the system.

Within this predetermined blog with x,y,z plugins, sold at a fixed/unchangeable price, I want to, as the admin, sell to everyone's referrals (to infinity) an upgrade package that provides additional themes, plugins, etc. This will be how I monetize the system.

Recap: I let everyone sell my blog and anyone who buys it from anyone else can then in turn sell it, this can continue to infinite depth... Anyone who buys it can sell it and they receive 100% paid directly to their PayPal. I then have access to sell to all referrals to infnity an upgraded version, which is how I will monetize my blog.

Thank you for your help.