You just don't get it.
Why work to design, produce and market something you don't make right now? You act like he has unlimited time. He's allowed to eat, sleep, race his cars and do whatever else he wants vice spending 24 hours a day on rocketry.
Marketing alone doesn't predict success. The first step is to have something everyone wants (not just a few people). Then maybe you'll have something marketing can do something with. You'd never be able to sell ice at the south pole, regardless of the marketing.
You're best bet is to learn how to make one yourself. At least this way your energies would go to the goal and not to tilting at windmills