How do I become a famous/successful actress/singer?? please answer if you can help!?

I'm 18, a senior in high school, and I've decided I want to pursue acting and singing. I have a good voice but haven't really had training or lessons or anything, and people say I'd be a good actress. Problem is, I've been involved in other things in school, but never did the school plays or anything like that so I have little/no experience, which probably won't get me anywhere. I really want to do this for a living, but I don't know where to start. Who do I contact? I live in a big city but its not LA or anything so who is there to 'discover' me? how do people go about getting record deals, being on tv shows, movies, etc? I really want to do this but I'm scared I'm too old to start this and I really want to do it! (my parents aren't supportive but I know I could do it if I had the right support, preparation, etc!! I just don't know where to start!) thanks so much! please give as much advice as possible. I'm definitely going to college, but should I pick one in nyc or la? I want to be like mandy moore or something. she is an actress who sings too and she isn't so famous that she's always talked about but people know who she is because of her work...but how do I even get anywhere with this? please answer and thank you for your help!