Is this a trick question?

Why not use this opportunity to create a business that actually brings in some money, in other words, totally unrelated to the music business and then do the audio thing on the side, since you're saying you still need a lot to learn about audio engineering, in one of the wings of the mansion your pops-in-law is certainly going to give you two after the wedding?

Reason why I say this is because bottom line, if your wife's father is willing to invest in you to start a business that will eventually sustain your wife and children, I don't know man, but I'd be considering a business that generates more money than audio engineering, especially when you have no experience in an industry where many professionals are leaving the commercial 9-5 setting, and doing it from their homes.

I'd personally look into Franchising. When you have a ton of money, this is an option where you can invest the money and almost let the franchises run themselves (since you're constantly guided by the corporate entity).