This is really important dilemma in our lives. I think we, as humans should support people who want to follow dreams, because that's the only way to improve our world. If someone wants to be engineer, just let him/her be. Don't restrict them from their dreams.
But life is difficult sometimes, so it doesn't give what we want to us. We will struggle in our lives many times that we can't even count. But don't let it put obstacles in your way. Tell your family that you want to be independent, but say thanks to them for everything they did for you. But if you want something for real and if you have problem about money, you should keep working all the time. Never give up on your dreams but keep working hard as well. And do it like an honourable person, don't choose bad way like some people choose to gain money, gambling for example.
And if you really want to do something in your life, just give up on unnecessary things that you usually do. For example, if you drink a lot, try to restrict it. If you like buying new clothes, try new things, try to combine clothes differently for example.
Those are my suggestions, you don't have to do them of course. But always look for other options in your life. I hope you will be happy with your choice.