How much equity should I give an engineer who I'm asking to join my company as a co-founder? (He'll be receiving a salary, too, and I'm self-funding)

I am currently a sole founder. I am not an engineer. This is a technical startup. So ideally I need a technical co-founder to join me. I'd been planning to just hire a couple engineers to build out the MVP, but this engineer and I really hit it off, and I'd like him to join the company as a co-founder. He also needs to be paid a full salary. I am self-funding the company to MVP on a bootstrapped budget. So two questions... 1. If he didn't need a salary, how much equity would you give him? (just looking for a range)? 2. Since he does need a salary, how much equity would you give him on top of the salary? (again, just a range, please)