The way the partner program works is that you build apps for people, and then they subscribe to the plan they need on Bubble themselves. The plan they pick depends on the number of workflows, whether they need SSL, etc.
On your part, it’s really up to you. You can charge a one time fee, or a monthly fee. We don’t interfere with this, the only thing we need is them to be on their own account. Once you’re done building, you invite them to their app through the collaboration section in the settings tab. You can keep the app on your account if they want to (so that you can maintain it), but it’s something you need to decide and talk about with your clients.
Let me know if you have more questions.