At 16 your signature is not legally binding which will be your number 1 issue. I know at 16 two years seems like an eternity but it will pass. During those two years you should be doing the following:
Learn as much as you can in the area you want to invest in.
Learn how to market yourself via social media and build a network of investors.
Find some other cash based business you can dabble in like gumball machines. No joke, it will teach you people skills, selling, follow up, budgeting, risk management, and making business focused decisions. All skills transferable to investing. Cost of entry is not significant and with 10 machines you could earn passive 200 or more a month depending on location.
Get a part time job that is close to what you want to do and learn. So if you want to flip homes, most high schools have a program you can earn credit with other students building homes. If you want to go into rentals, see if you can find work for some complex, a wholesaler, a job working for an agent could be help you learn.
Save money
Locate a mentor, not some guru you pay for but a real person with success in what you want to do. See if there is any assistant like work you could do for that mentor to add value and learn as you go. Like running around every Friday and Sunday putting up and taking down bandit signs or cold calling prospects or list/lead generation.
Learn accounting and book keeping, just do it, start now.