How much equity should I ask ? I will not promote

I will not promote. An ex-coworker of mine wanted me to join his startup. This is pre-seed, with zero customers. He already had the idea when he approached me and had built a very basic, unfinished backend that somewhat works, as well as a mobile app that doesn’t work well and is incomplete, not launched. I started helping him and built the web app for him from ground up, which will be where the majority of users are expected to engage. The plan is for me to rebuild the mobile app in React Native later on. I asked him for 15% equity as a co-founder; however, he countered with 2.5% to start, with the possibility of increasing my equity as we hit milestones. Here are some details: This app is for the school industry (can’t say specific industry ) , in which he has a lot of background knowledge. It is something new to me, so I am trying to learn. He also wants to onboard a few other co-founders from the industry since relationships, connections, and navigating policies are important in this industry. He said that if he gives me 15%, it will be hard to bring other people on board. He has a corporation registered under his name in the US, and he wants to create another company (this app) under that corporation in Canada. He plans to give me equity in this Canadian company since I live in Toronto. So the equity I will be getting will be subsidiary of the parent company that he completely owns. For me, I think I should get more than 2.5% to start. I have startup and big tech experience, with 3 years as a full-stack developer and 4 years as a front-end developer. I am currently senior at big tech. He also said we won’t be paying ourselves for a year or so, since he’s doing his masters and has a full time job aside from this start up. He recommended me doing my full time job while work on this part time. What do you guys think ? What else do I need to clarify? Thank you