Check what are people needs in this year or around people where you live, when you see there are many people have a same problem or want a something, you need to find the solution for that.
In the instance of Elon, it is not all about the money. Idea and smartness. There are people who has the money and not know how to multiply it.
Yep, there are many successful athletes and people who won lottery, but ended up become poor when they're old. They only know how to make money, how to save it and how to use it, but they forgot they need to invest or have a business.