It is hard trying to fund this hobby at a young age, I'm 18 and I am paying for college and i only have a part time job but with whatever leftover money i have i can save for new toys. Its not really possible to fund multiple projects for me so i only do one at a time and sometimes it takes a long time to get what you want finished but if your passionate about it it will get there.
Just like in earlier posts, start off a little smaller so you dont plunge into the hobby and find out its not for you. Buy a truck first and experience building it, and that could easily be done for under 600 bucks. In just about 3 years ive accumulated, 2 trucks, 4 trailers, and a skid steer. It takes alot of work, that's what my summer jobs usually fund but the hobby allows you to step out of reality for a while and enjoy operating the machinery. If you set a goal and you are determined to reach it, you will. I did it a few years ago, so from one young hobbyist to another good luck and hopefully something will fall into place
Happy Hunting
J.D.