It's tough to get where you want to go starting from where you are. Indiana is a pretty 17th-century state; you do not want to get busted there. It can ruin your life in many ways, and a felony conviction for growing weed can make it impossible to work in the legal industry in other states or countries.
It's one of those things where there really are no easy shortcuts; if it were that easy, everyone would already be doing it.
Since Indiana is illegal as hell, at some point, following your dream is going to require leaving Indiana. The question is, do you go now and start from scratch in a legal state out west, or gain some experience first and then take that experience to a legal state and use it to get in the door out there. Both have advantages and disadvantages.
If you go now and move to say, Colorado, you're going to be competing for the same beginners' opportunities that a million other kids from all over the country are moving there to chase. Most of them have at least some experience under their belt, and they're still having a tough time making it. You might want to do some research (if you haven't already) on marijuana migration into legal states, and how hard it can be to move out there and start from square one all on your own.
But if you stay in Indiana, you're faced with either breaking the law to get your experience, or getting your horticultural experience in non-cannabis industries. But at least you have the safety net of living with your parents while you work in a nursery, or whatever. By the way, do they know about this goal? Are they supportive? Would they help you out with some money to move and get started?
Keep in mind that the legal cannabis industry is becoming so mainstream and corporate, general horticultural experience is increasingly useful as a starting point in the industry. As far as the horticultural field is concerned, it's mostly just another plant. If you know how to work in a nursery or a greenhouse, you're a big step ahead of a kid who moved to Colorado after doing two or three 1-plant grows in his closet.
One other thing to consider... what part of Indiana are you from? Michigan is going to be somewhat legal by next year, so you might be able to get established there without having to move far. Or, you might be able to catch on with a commercial hemp farm in Kentucky. It's just general farm work, but you're farming weed. Have you considered those ideas?