Julie here from Shopify Support.
Assuming you've created the development store under your Shopify Partners account and have transferred ownership to your client, you will be eligible to earn recurring revenue based off your client's subscription. If they paid upfront for the biennial plan, you'll still earn monthly revenue; the total revenue share will be 20% of the monthly discounted rate, paid to you monthly.
As you hand off your development stores to clients, I suggest sharing our Merchant Handoff Kit. This kit should help answer any questions your clients have about running their online store or managing their POS. It includes links to step-by-step instructions for all the most common tasks they'll be doing, and issues they may face while managing their new store. We are currently updating the Merchant Handoff Kit, so stay tuned for an updated copy shortly.
Congratulations on completing your development store! Let me know if you have any further questions.