I would call them business plans rather than schemes, but your estimate of time to payoff is reasonable. First delivery of material mined from asteroids would be 20 years from project start if all goes well. Would your credit union would be interested?
It is because of your intense interest in space commercialization that I hoped you would have some insight into how investors viewed the "risk" of improved propulsion!
And yet I used an obvious "hot-button" word like like "scheme" :-(