I'd be keen to know specifically how your cousin is worth a billion dollars. Because there's no faster way to be rich than to model.
Ok, 15 years is a LONG time. A DAMN LONG time. Set 3 to 5 year goals max and make as damn sure you HIT them. Your whole world will change in 15 years.
Who doesn't want Passive Income? I mean money while you sleep? Honestly. How much? from what sources? how are you going to do it? How many ways are there to earn passive income? Read multiple streams of income by Robert Allen for e.g. Think house, shares, business, franchise, art, investment, gold etc. Think investment all the time.
Don't want to work anymore? Try not working for a month and tell me how bored you get. Your mind must always be active, be creative, chasing for a new challenge. Retire by 45? Fuck that, I'm not retiring I'm going to work on myself and my passions and my family for every single day of my life. Whether I work for someone or myself, my reputation, who I am and my legacy are FAR more important. I have a job, I have investments, I know who I want to be, what sort of mark I want to leave on society. Work on that. Else it's just words on a forum...
Invest money to fill your head with knowledge, then meet people, expand your knowledge, learn to lose money, learn from your mistakes, become more adept. The most successful people aren't the ones that don't fail, they are the ones that fail all the time but get better and better at finding a solution and resolving matters by themselves. They are also willing to take big risks. I want to be Donald Trump, but I know I can't risk things like him, so i'll never be him. I'll be better than me now but never better than someone who's willing to risk more. Fact.
Manage your emotions. This is priceless. Find a way to be calm in a storm and ready to turn on the heat when required.