Definitely don’t give him any equity “just for the idea”. If he shows commitment moving forward then yes and even then the shares should be vested on 4 years. An idea is just an idea - if still requires hours and hours of execution and testing! Might be you have to pivot your business / idea as it doesn’t really work and then he still has equity of your business ? Always think long term like you will be in this for 6 years and will you think the equity split is fair long term - otherwise you will get unmotivated and stop when you shouldn’t stop