I've earlier seen this with tools like Punchtab and WooCommerce. This is a great idea and I'm glad you're working on this.
The best live example of this is BigRock's 10% when you share on Twitter or Facebook.
A big problem here would be that users want "instant gratification" - like in BigRock's case. Users don't want to wait for a friend to buy something to become eligible for a discount. This is one of the reasons that people identified your idea as a affiliate marketing channel. If you have seen Cashkaro or Nectar, it lets you get a cashback from the affiliate commission they will earn from merchants.
Example: Flipkart gives me 10% affiliate commission, I offer users to buy using my link and get a 5% discount code/cash back.
A good implementation for your network would be to reward users instantly on sharing (this will be your cost). You can then keep the benefits earned from their shared links.
Let me know if you have questions.