Good you walked away. In my experience, the heavy lifting in a tech start up is, by definition, the tech. The "idea guys" rarely understand that it's the execution that makes an idea valuable.

Sales are important, but are a bit of a crapshoot. You can't consistently sell trash, no matter how good a salesperson you are. The guy was happy to roll the dice, while using your mental energy. Great deal for him, but not so good for you. You risk the burnout, stress and pressure, while he feeds you requirements and deadlines, and essentially becomes your manager.

In my younger days I got a lot of similar proposals, but thankfully could see right through them from day one. Bootstrapping as a solo founder was the harder, but ultimately more rewarding route for me.